WO2023074909A1 - Polyimide porous film, electrode structure, and power storage device - Google Patents

Polyimide porous film, electrode structure, and power storage device Download PDF

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WO2023074909A1
WO2023074909A1 PCT/JP2022/040857 JP2022040857W WO2023074909A1 WO 2023074909 A1 WO2023074909 A1 WO 2023074909A1 JP 2022040857 W JP2022040857 W JP 2022040857W WO 2023074909 A1 WO2023074909 A1 WO 2023074909A1
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porous film
polyimide porous
film
lithium
polyimide
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PCT/JP2022/040857
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French (fr)
Japanese (ja)
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武治 福澤
智哉 二村
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株式会社スリーダムアライアンス
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to polyimide porous films, electrode structures, and electricity storage devices.
  • lithium-ion batteries and capacitors have become widespread.
  • technologies such as lithium ion batteries and lithium ion capacitors using graphite as a negative electrode and lithium metal batteries using metallic lithium as a negative electrode have been remarkably developed.
  • These electric storage devices have a structure in which a positive electrode, a separator, and a negative electrode are stacked in order and filled with an electrolytic solution, and the positive electrode and the negative electrode are insulated by the separator. Alloys with other metals, carbon and graphite are often used.
  • Patent Document 1 a porous film made of a polyimide material with relatively high heat resistance as an insulating separator has been studied.
  • a polyimide porous film as described in Patent Document 1 can be used as a separator for an electricity storage device, but there is a demand for higher performance of an electricity storage device incorporating a polyimide porous film as a separator.
  • a first object of the present invention is to provide a polyimide porous film suitable as a separator for an electric storage device such as a lithium ion battery or a lithium metal battery and an electrode structure used therein.
  • the present inventors have made intensive studies, and produced polyamic acid for forming a polyimide porous film from an appropriate carboxylic acid and diamine, thereby producing lithium ion batteries, lithium metal batteries, and the like. We have found that the initial charge/discharge characteristics of an electricity storage device can be improved.
  • a second object of the present invention is to provide a polyimide porous film that is well-balanced and excellent in film strength, not only for use in electrode structures and electricity storage devices. In particular, a certain degree of film strength can be maintained without depending on the first invention.
  • the polyimide porous film of the first invention has the following configurations [1] to [5].
  • a polyimide porous film comprising a copolymer of a carboxylic acid and a diamine, having a large number of pores, and containing dimethylbenzidine as the diamine.
  • Dimethylbenzidine includes 2,2'-dimethylbenzidine and 3,3'-dimethylbenzidine, of which 2,2'-dimethylbenzidine is preferred.
  • the polyimide porous film of the present invention reduces the amount of reaction with lithium, and when the polyimide porous film of the present invention is used in a lithium ion battery or a lithium metal battery, deterioration of coulombic efficiency can be suppressed.
  • [2] It is characterized by containing at least one of pyromellitic dianhydride and biphenyltetracarboxylic dianhydride as carboxylic acid.
  • pyromellitic dianhydride and biphenyltetracarboxylic dianhydride may be blended and used, the strength of the polyimide porous film can be improved by combining dimethylbenzidine with pyromellitic acid.
  • the pore size of the pores of the polyimide porous film of the present invention is preferably 800 nanometers or less.
  • the pore diameter of the pores is preferably as small as possible, more preferably 700 nm or less, and even more preferably 600 nm or less.
  • the maximum stress of the polyimide porous film of the present invention is 25 N/mm 2 or more.
  • the method and conditions for measuring this maximum stress are as described later.
  • the breaking energy of the polyimide porous film of the present invention is 0.34 J/mm or more.
  • the method and conditions for measuring the breaking energy will also be described later.
  • the present invention makes it possible to provide a polyimide porous film having a maximum stress of 25 N/mm 2 or more and a breaking energy of 0.34 J/mm or more, which was conventionally difficult.
  • lithium reacts or adsorbs to the polyimide porous film during initial charging and discharging. can be reduced, and the initial charge/discharge characteristics can be improved.
  • the polyimide porous film of the present invention has the following configuration: It is characterized by comprising a copolymer of a carboxylic acid containing both biphenyltetracarboxylic dianhydride and pyromellitic dianhydride and a diamine containing both paraphenylenediamine and oxydianiline.
  • the molar ratio of biphenyltetracarboxylic dianhydride and pyromellitic dianhydride is preferably 1:1, but this ratio may vary slightly and is preferably set in the range of 4:6 to 6:4.
  • the molar ratio of p-phenylenediamine and oxydianiline is preferably 1:1, but this ratio is also preferably 4:6 to 6:4.
  • diamine dimethylbenzidine may be used in combination.
  • the countless pores formed in the polyimide porous film of the present invention can be formed by removing fine particles previously mixed in a slurry containing polyamic acid during firing.
  • the polyimide porous film using a polyamic acid formed from a carboxylic acid and a diamine of the present invention reacts or reacts with lithium as compared with a conventional polyimide porous film, especially a polyimide porous film using biphenyltetracarboxylic acid as a carboxylic acid.
  • the amount to be adsorbed can be reduced.
  • the amount of lithium that reacts with or adsorbs to the polyimide porous film, which is the separator can be reduced in the early stages of charging and discharging of the electrical storage device, and the initial charging and discharging behavior can be improved.
  • FIG. 2 is a cross-sectional view of a laminate produced for measuring the amount of lithium that reacts with or adsorbs to a polyimide porous film, cut along a plane substantially perpendicular to the polyimide porous film.
  • the polyimide porous film of the present invention will be described below.
  • the polyimide porous film of the present invention composed of a copolymer of carboxylic acid and diamine may be used as a separator for an electric storage device such as a lithium ion battery, a lithium metal battery, or a capacitor, or may be used for other purposes. There is no limit to the usage.
  • the porosity by weight method is preferably 45 to 75%, and the Gurley value (air permeability) is preferably 300 seconds or less. If the porosity is 45% or more, the Gurley value can be 300 seconds/100cc or less at a film thickness of 20 ⁇ m, for example, and it is possible to provide a separator that is preferable not only from the viewpoint of the Li reaction amount described later but also from the viewpoint of the Gurley value. can.
  • the Gurley value can be reduced by increasing the porosity, the film strength of the polyimide porous film is weakened as the porosity is increased, for example, the porosity exceeds 70%. For this reason, the film may be damaged during actual battery production, and it is difficult to assemble a battery using a polyimide porous film with an increased porosity of 80% or more.
  • the thickness of the polyimide porous film is preferably, for example, about 4 ⁇ m to 50 ⁇ m. If the thickness of the polyimide porous film is too thick, there is a tendency for the ionic conductivity to decrease. It is also related to short-circuit resistance, and there is a tendency that the thinner the film, the more difficult it becomes to maintain the insulation. On the other hand, if the polyimide porous film is too thin, the film strength will decrease. Also, the maximum stress of the polyimide porous film is preferably 25 N/mm 2 or more.
  • the film can be produced by the following steps: A step of mixing fine particles for opening holes into a polyimide precursor solution containing polyamic acid (so-called polyimide varnish) from a carboxylic acid anhydride and an organic amine compound to prepare a slurry; a step of forming the prepared slurry into a thin film on a support to form a non-porous raw fabric; A step of peeling the raw fabric from the support, A step of firing the original fabric to make it porous.
  • the removal of fine particles for forming pores and the imidization of the raw fabric can be carried out in parallel, but it is also possible to remove the fine particles from the raw fabric, open the pores, and then imidize the raw fabric.
  • a polyimide precursor solution includes a polyamic acid made from a carboxylic anhydride and an organic amine compound.
  • a polyamic acid or a mixture of a polyamic acid and a solvent is used as a polyimide precursor solution, and fine particles for opening are mixed into the polyimide precursor solution to prepare a slurry.
  • the polyimide precursor solution may be a solution obtained by polymerizing a tetracarboxylic dianhydride and a diamine in the presence of an organic solvent, or a solution obtained by dissolving a polyamic acid in an organic solvent. But it doesn't matter which.
  • a slurry for forming a film is prepared by mixing a polyimide precursor solution, fine particles for opening holes, a dispersant, a solvent, and the like. By forming this slurry into a thin film, a non-porous raw fabric can be produced.
  • a dispersant is not essential, and may be used as appropriate.
  • the material of the fine particles for opening holes may be any material as long as it is insoluble in the organic solvent used for the polyimide precursor solution and can be selectively removed after film formation.
  • fine particles composed of an inorganic material include metal oxides such as silica (silicon dioxide), titanium oxide, and alumina (Al2O3).
  • Fine particles composed of organic materials include polyolefins such as polypropylene and polyethylene, polystyrene (PS), acrylic resins (e.g., methyl methacrylate, isobutyl methacrylate, polymethyl methacrylate (PMMA), etc.), polyurethane resins (PUR), Melamine resin (MF), urea resin (UF), phenol resin (PF), epoxy resin, cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetate (PVAc), ABS resin, AS resin, polyacrylonitrile (PAN), polycarbonate ( (PC), polyamide (PA), polyethylene terephthalate (PET), polyester, polyether, and other organic polymers (hereinafter referred to as resin fine particles).
  • PS polystyrene
  • acrylic resins e.g., methyl methacrylate, isobutyl methacrylate, polymethyl methacrylate (PMMA), etc.
  • PUR polyurethane resins
  • the shape of the fine particles is not limited, spherical or approximately spherical shapes are desirable. Basically, a shape close to a true sphere is desirable, but a substantially spherical shape such as an ellipse having some distortion, fine irregularities, etc. may also be used. Further, fine particles having a nearly spherical shape and a small particle size distribution index (small variation in particle size) are preferable. By using fine particles satisfying these conditions, it is possible to reduce the variation in pore size formed in the polyimide porous film. As a result, when the polyimide porous film is used as a separator of an electric storage device, lithium can be moved more uniformly on the separator.
  • the particle size of the fine particles it is preferable to use those having a particle size of 800 nm or less. Thereby, the pore diameter of the porous film obtained by removing the fine particles can be made 800 nm or less. More preferably, the particle size of the fine particles is 600 nm or less, more preferably 500 nm or less.
  • a dispersant may be added to the polyimide precursor solution for the purpose of uniformly dispersing the fine particles in the polyimide precursor solution.
  • a dispersant By adding a dispersant, the polyamic acid and the fine particles can be mixed more uniformly, and the fine particles can be more uniformly distributed in the raw fabric described later.
  • the polyimide porous film obtained by finally removing the fine particles can have a more uniform pore distribution.
  • Carboxylic anhydride and polyamic acid As the polyamic acid, those obtained by polymerizing a carboxylic acid dianhydride and a diamine can be used.
  • the amount of the carboxylic acid dianhydride and the diamine to be used is not particularly limited, but the diamine is preferably 0.50 to 1.50 mol, and 0.60 to 1.30 mol, per 1 mol of the carboxylic dianhydride. More preferably, 0.70 to 1.20 mol is particularly preferred.
  • the carboxylic acid dianhydride may be appropriately selected from those conventionally used as raw materials for synthesizing polyamic acids.
  • the carboxylic dianhydride may be either an aromatic tetracarboxylic dianhydride or an aliphatic tetracarboxylic dianhydride. Preference is given to using dianhydrides. Two or more carboxylic acid dianhydrides may be used in combination.
  • aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 3,3′,4,4 '-biphenyltetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4- Dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3 ,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3 ',4,4'-benzoph
  • aliphatic tetracarboxylic dianhydrides include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 1, 2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride and the like. It is particularly preferable to include at least one of pyromellitic dianhydride and biphenyltetracarboxylic dianhydride as the carboxylic dianhydride. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.
  • the diamine which is an organic amine compound, may be appropriately selected from diamines conventionally used as raw materials for synthesizing polyamic acids.
  • the diamine may be either an aromatic diamine or an aliphatic diamine, and can be appropriately selected in view of the properties of the intended polyimide resin, but the aromatic diamine is preferred. Moreover, you may use a diamine in combination of 2 or more types.
  • aromatic diamines include phenylenediamine and its derivatives, diaminobiphenyl compounds and their derivatives, diaminodiphenyl compounds and their derivatives, diaminotriphenyl compounds and their derivatives, diaminonaphthalene and its derivatives, aminophenylaminoindane and its derivatives, diaminotetra
  • aromatic diamines include phenylenediamine and its derivatives, diaminobiphenyl compounds and their derivatives, diaminodiphenyl compounds and their derivatives, diaminotriphenyl compounds and their derivatives, diaminonaphthalene and its derivatives, aminophenylaminoindane and its derivatives, diaminotetra
  • examples include phenyl compounds and derivatives thereof, diaminohexaphenyl compounds and derivatives thereof, cardo-type fluorenediamine derivatives and the like.
  • diamines based on the number of benzene nuclei are the following 1) to 3): 1) Benzenediamine having one benzene nucleus, such as 2,4-diaminotoluene, phenylenediamine, and 2,6-diaminotoluene.
  • diamines having three or more benzene nuclei 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1, 4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3′-diamino-4-(4-phenyl)phenoxybenzophenone, 3,3′-diamino-4,4′-di( 4-phenylphenoxy)benzophenone, and the like.
  • the reaction of tetracarboxylic dianhydride and diamine is generally carried out in an organic solvent.
  • the organic solvent used for the reaction of the tetracarboxylic dianhydride and the diamine is particularly capable of dissolving the tetracarboxylic dianhydride and the diamine and not reacting with the tetracarboxylic dianhydride and the diamine. Not limited.
  • the organic solvent may be used alone or in combination of two or more, and may be selected as appropriate.
  • organic solvents used in the reaction between tetracarboxylic dianhydride and diamine include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, and N,N-dimethylformamide.
  • the amount of the organic solvent used is not particularly limited, it is desirable that the content of the polyamic acid to be produced is 5 to 50% by mass.
  • Any organic solvent may be used for the polyimide precursor solution as long as it dissolves the polyamic acid or polyimide resin used but does not dissolve the fine particles.
  • the content of the organic solvent in the polyimide precursor solution is preferably 50 to 95% by mass, more preferably 60 to 85% by mass.
  • the solid content in the polyimide precursor solution is preferably 5 to 50% by mass, more preferably 15 to 40% by mass.
  • Antistatic agents, flame retardants, chemical imidizing agents, condensing agents, release agents, surface control agents , a dimensional stabilizer, etc., may be mixed as appropriate.
  • more specific manufacturing procedures for the polyimide porous film are as follows (1) to (6) below. Since it is necessary to immerse the original sheet in a solvent to remove the inorganic particles, it is difficult to perform the porosification process and the baking process at the same time. In this case, it is desirable to perform the porosification step before the firing step. On the other hand, when resin particles are used to make the original fabric porous, the porous making process and the baking process can be performed simultaneously, and the manufacturing process can be simplified or made more compact.
  • the manufacturing procedure of polyimide porous film is as follows: (1) preparing a polyimide precursor solution having a polyamic acid synthesized from a carboxylic anhydride and an organic amine compound; (2) a step of preparing a slurry by mixing a polyimide precursor solution and fine particles; (3) a raw fabric forming step of coating the slurry on a support to form a non-porous raw fabric; (4) A peeling step of peeling off the original film formed in the original film forming step from the support; (5) a porosification step of making the original sheet peeled from the support by the peeling step porous; and (6) a baking step of baking the original sheet.
  • polyamic acid can be obtained by polymerizing a carboxylic acid dianhydride and an organic amine compound. By applying heat to the polyamic acid to imidize it (thermal imidization), or by chemically imidizing the polyamic acid (chemical imidization), the carboxylic acid moiety can be ring-closed to form a polyimide. .
  • the imidization rate is desirably about 80% or more, preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more, but this may also be adjusted according to the desired physical properties.
  • Carboxylic anhydrides and diamines mentioned above can be used, but for preparing the polyamic acid used in the polyimide porous film of the present invention, the diamines are phenylenediamine, dimethylbenzidine, diaminodiphenylmethane, diamino It is preferably at least one selected from dimethyldiphenylmethane, o-dianisidine and 9,9-bis(4-aminophenyl)fluorene, with dimethylbenzidine being particularly preferred.
  • the carboxylic acid can be selected from pyromellitic dianhydride, biphenyltetracarboxylic acid, oxydiphthalic anhydride, benzophenonetetracarboxylic dianhydride, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride.
  • pyromellitic dianhydride biphenyltetracarboxylic acid
  • oxydiphthalic anhydride oxydiphthalic anhydride
  • benzophenonetetracarboxylic dianhydride benzophenonetetracarboxylic dianhydride
  • 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride.
  • the benzophenonetetracarboxylic dianhydride 3,3′,4,4′-benzophenonetetracarboxylic dianhydride is preferred. That is, the carboxylic acids include pyromellitic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 9,9-bis(3,4 -Dicarboxyphenyl)fluorene dianhydride is preferably at least one selected from.
  • diamines among o-phenylenediamine, m-phenylenediamine and p-phenylenediamine, m-phenylenediamine and p-phenylenediamine are preferable as phenylenediamine, and p-phenylenediamine is more preferable.
  • dimethylbenzidine 2,2'-dimethylbenzidine is preferred among 2,2'-dimethylbenzidine and 3,3'-dimethylbenzidine.
  • Diaminodiphenylmethane includes 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenylmethane is preferred.
  • Diaminodimethyldiphenylmethane is preferably 4,4'-diamino-3,3'-dimethyldiphenylmethane.
  • the diamines are p-phenylenediamine, 2,2′-dimethylbenzidine, 4,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′-dimethyldiphenylmethane, o-dianisidine, 9,9 At least one selected from -bis(4-aminophenyl)fluorene is desirable.
  • One type of diamine may be used, or two or more types may be mixed.
  • an organic polar solvent can be used as the solvent for polymerizing the polyamic acid.
  • Preferred organic polar solvents include, for example, tetramethylurea, phenol, N-methyl-2-pyrrolidone (NMP) , pyridine, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, p-chlorophenol, o-chlorophenol, dimethylsulfoxide, and cresol.
  • conditions for producing the polyamic acid include, for example, approximately equimolar (substantially equimolar) amounts of tetracarboxylic dianhydride and diamine, preferably about 80° C. or lower, more preferably 70° C. or lower, and still more preferably should be reacted at a temperature of 0 to 65°C, preferably 10 to 60°C.
  • the reaction time is preferably about 0.1 hour or more, more preferably 0.2 to 72 hours, and still more preferably 0.5 to 60 hours, whereby a polyamic acid can be produced.
  • a component for adjusting the molecular weight can also be added to the reaction solution when producing the polyimide precursor solution.
  • the prepared polyimide precursor solution comprises, for example, 5 to 50% by mass of polyamic acid and 50 to 95% by mass of organic polar solvent. If the content of the polyamic acid is less than 5% by mass, the film strength of the porous polyimide film produced is reduced, and if it exceeds 50% by mass, the viscosity of the porous polyimide film becomes too high, resulting in poor handleability.
  • a slurry is prepared by mixing the polyimide precursor solution and the fine particles described above. Additives such as an organic solvent for concentration adjustment, antistatic, low-temperature baking, releasability, coatability, low hygroscopicity, low coefficient of linear expansion, and chemical imidizing agents can be added to the slurry. good.
  • the slurry contains 5 to 90% by mass of the polyimide precursor solution, 2 to 40% by mass of fine particles for opening, 0 to 95% by mass of an organic solvent for adjusting the concentration, and the additive is not particularly limited, but preferably 0 to 20% by mass. which are mixed with an agitator. For stirring, it is recommended to use a rotation-revolution stirrer such as "Awatori Mixer" (manufactured by Thinky Co., Ltd.).
  • the solution viscosity of the slurry should be determined appropriately according to the characteristics of the die and coater machine used for coating. For example, from the viewpoint of ease of coating and film strength, various Can be used in dies and coater machines.
  • the produced slurry can be coated on a support to form a raw fabric.
  • the coating method is not particularly limited.
  • a slurry blade, a T-die, or the like is used to coat a support such as a glass plate, a stainless steel plate, a PET (polyethylene terephthalate) film, a PEN (polyethylene naphthalate) film, or the like. do.
  • a resin film may be used in addition to an endless mechanism such as a metal belt. Any support may be used as long as it is unaffected or hardly affected by the prepared slurry.
  • the endless mechanism is made of metal such as stainless steel, and the resin film is made of resin such as PET or polytetrafluoroethylene. should be used.
  • the length of the original fabric is not particularly limited, but from the viewpoint of productivity, it is preferably long (for example, 5 m or longer), more preferably 10 m or longer, and even more preferably 20 m or longer.
  • the upper limit of the length of the original fabric is not particularly limited, it is, for example, 4000 m or less, and typically 1000 m or less facilitates handling of the original fabric. It is preferable to properly dry the original sheet in order to separate the original sheet from the support more easily.
  • a polyimide porous film having spherical or approximately spherical pores can be produced by selecting an appropriate method to remove the fine particles from the raw film peeled from the support.
  • methods for removing fine particles there are a method of removing fine particles by dissolving them with a solvent, an acid or an alkali, and a method of removing fine particles by firing, but this depends on the fine particles used.
  • resin particles are preferable as fine particles for forming pores.
  • inorganic particles such as silica are used as the open-pore particles, they can be removed by bringing them into contact with acid or alkali to dissolve the inorganic particles.
  • the resin particles can be dissolved and removed with an organic solvent in which the resin particles are soluble but the polyimide film is not dissolved.
  • organic solvents include ethers such as tetrahydrofuran; aromatics such as toluene; ketones such as acetone; and esters such as ethyl acetate. Among these, ethers such as tetrahydrofuran are preferred, and tetrahydrofuran is more preferred.
  • openings can be formed by heating to a temperature equal to or higher than the thermal decomposition temperature of the fine resin particles and lower than the thermal decomposition temperature of the polyimide resin to decompose and remove the fine resin particles. .
  • thermal imidization Heat is applied to the obtained raw film or porous raw film to imidize it (hereinafter referred to as thermal imidization), whereby a polyimide porous film can be formed.
  • the shrinkage rate in the machine direction (MD direction) of the polyimide porous film after thermal imidization should be suppressed to 5% or less, and the shrinkage rate in the width direction (TD direction) should also be suppressed to 5% or less.
  • the temperature conditions are, for example, a temperature range of 250 to 500° C.
  • the heating rate in the temperature range of 200° C. or higher is 20° C./min or more, preferably 30° C./min or more.
  • the porous polyimide film of the present invention having significantly improved surface open area ratio and pore size can be obtained by heating at the above-described temperature increase rate in the temperature range of 100 to 250° C. where the imidization reaction occurs remarkably.
  • the firing temperature varies depending on the type of polyamic acid and the intended degree of imidization, but is preferably 120 to 500.degree.
  • the drying step and the firing step may be separated, but they may be carried out without strict separation.
  • firing at 360 ° C. a method of continuously raising the temperature from room temperature to 360 ° C. and then firing at 360 ° C. for several tens of minutes, or a method of stepwise raising the temperature from room temperature to 360 ° C. and firing at 360 ° C.
  • there is a method of firing for several tens of minutes it is preferable to select a suitable procedure.
  • the raw fabric may be peeled off from the support at an appropriate timing while the temperature is being raised from room temperature.
  • the baked polyimide porous film is preferably wound around a winding core having a diameter of 2.5 cm (1 inch) or more and 25 cm (10 inches) or less.
  • the diameter of the winding core is preferably 5 cm (2 inches) or more and 10 cm (4 inches) or less.
  • the material of the winding core is not particularly limited, but includes paper, metal such as stainless steel, and hard plastic such as ABS, PP, PE, PVC, PET, FRP, and bakelite.
  • the decomposition temperature of the fine resin particles is preferably, for example, 120° C. or higher and 500° C. or lower.
  • alkali etching is performed in order to remove at least part of the original film before removing the fine particles, or to remove at least part of the polyimide porous film after removing the fine particles.
  • the polyimide porous film produced by the above procedure has a plurality of spherical or substantially spherical pores formed therein, and at least some of the pores communicate with each other.
  • the pore size on the surface and inside of the polyimide porous film can be controlled by appropriately selecting or adjusting the type and size of fine particles used when producing the film.
  • the pore diameters are less varied and have a more uniform distribution.
  • a method of measuring the Gurley value of the film at several points at different locations and evaluating the variation in the values at that time can be used.
  • the air permeability (number of seconds for 100 mL of air to pass through the film) is measured by the Gurley method, and the average value and standard deviation of the air permeability can be asked for.
  • a film having pores with small variations in pore size and distribution can be produced by using fine particles with a high sphericity and a small particle size distribution index, or by using a polyimide precursor containing fine particles and a polyamic acid or polyimide resin. It can be manufactured by adjusting the viscosity of the solution to an appropriate viscosity that enables uniform coating.
  • the air permeability measured by the Gurley method as described above is preferably 400 seconds or less, more preferably 300 seconds or less, and even more preferably 250 seconds or less. It is considered that such an air permeability allows lithium and lithium ions to move with lower resistance.
  • the film thickness of the polyimide porous film of the present invention is preferably 2 ⁇ m or more and 100 ⁇ m or less, more preferably 3 ⁇ m or more and 80 ⁇ m or less, and even more preferably 4 ⁇ m or more and 50 ⁇ m or less.
  • the film thickness can be obtained by measuring the thickness at a plurality of locations with a micrometer or the like and averaging the thickness.
  • the polyimide porous film of the present invention can be used as a separator in electricity storage devices such as nickel-cadmium batteries, nickel-hydrogen batteries, lithium-ion primary/secondary batteries using graphite for the negative electrode, and lithium-metal primary/secondary batteries using metallic lithium for the negative electrode. can be used. Among these, it is preferable to use it as a separator for a lithium ion secondary battery or a lithium metal secondary battery.
  • the polyimide porous film of the present invention may also be used as an electrolyte membrane for fuel cells or as a substrate for electronic circuits.
  • a power storage device using the polyimide porous film of the present invention as a separator includes a separator, a negative electrode, a positive electrode, and an electrolytic solution.
  • Electricity storage devices come in a variety of formats, including a wound type (cylindrical or rectangular in appearance), a laminate type, and a coin type. , and the electrolyte is injected into the exterior body to fabricate an electricity storage device.
  • the negative electrode of a lithium-ion battery has a structure in which, for example, a negative electrode mixture consisting of a negative electrode active material, a conductive aid, and a binder is formed on a current collector.
  • a material that can be electrochemically doped with lithium can be used as the negative electrode active material, and examples of such an active material include carbon materials, silicon, aluminum, tin, and Wood's alloys.
  • metallic lithium is used as the negative electrode, as is well known.
  • Carbon materials such as acetylene black and ketjen black are examples of the conductive aids that make up the negative electrode.
  • the binder is made of an organic polymer, and examples thereof include polyvinylidene fluoride, carboxymethyl cellulose, and the like.
  • a copper foil, a stainless foil, a nickel foil, or the like can be used as the current collector.
  • the positive electrode can have a structure in which a positive electrode mixture comprising a positive electrode active material, a conductive aid, and a binder is formed on a current collector.
  • a positive electrode active material nickel hydroxide can be used in the case of nickel-cadmium batteries, and nickel hydroxide or nickel oxyhydroxide can be used in the case of nickel-hydrogen batteries.
  • the positive electrode active material include lithium-containing transition metal oxides. , LiCo0.5Ni0.5O2, LiAl0.25Ni0.75O2, and the like. Carbon materials such as acetylene black and ketjen black can be used as conductive aids.
  • a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent is typically used as the electrolyte for a lithium ion battery or a lithium metal battery, but an aqueous electrolyte may be used depending on desired characteristics.
  • Lithium salts include LiPF 6 , LiBF 4 , LiClO 4 , LiFSI and the like.
  • non-aqueous solvents include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ⁇ -butyrolactone, vinylene carbonate, etc. These may be used alone or mixed with additives. good too.
  • Exterior materials include metal cans, aluminum laminate packs, and the like. Batteries may be rectangular, cylindrical, coin-shaped, or the like, and the separator of the present invention can be suitably applied to any shape. As an example, the procedure for producing a laminate type battery, a cylindrical battery, and a coin battery will be described below.
  • [Laminated Lithium Ion Secondary Battery and Lithium Metal Secondary Battery] [Positive electrode/negative electrode] Commercially available products can be used as the positive electrode and the negative electrode.
  • the positive electrode active material contained in the positive electrode is Li 1.1 Mn 1.9 O 4 having a spinel structure, and lithium-nickel-cobalt-lithium manganate ( Ni/Li molar ratio of 0.7), polyvinylidene fluoride can be used as the binder, and carbon black powder can be used as the conductive aid.
  • Graphite or the like can be used as a negative electrode active material for the negative electrode, and the porosity and pore diameter of the positive electrode active material layer and the negative electrode active material layer can be adjusted as appropriate.
  • the active material layer on one side of the current collectors of the positive electrode and the negative electrode is peeled off, and cut into a size of 29 mm ⁇ 40 mm, for example, for use.
  • a metal lithium layer can be formed with a predetermined thickness and used as the negative electrode. In this case, an improvement in energy density can be expected.
  • An aluminum positive electrode tab is welded to the positive electrode current collector of the positive electrode, and a copper negative electrode tab (negative electrode current collector plate) is welded to the negative electrode current collector of the negative electrode.
  • the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode, to which these tabs are welded, are opposed to each other, and a separator is sandwiched therebetween to form one plate-shaped electrode structure.
  • the above-described electrode structure is sandwiched using an exterior material (size and shape is, for example, a square of 60 mm ⁇ 60 mm) made of a laminate film provided with an aluminum layer, and three of the four sides of the square are heat-sealed by pressure bonding. It stops and forms an exterior body.
  • An electrolytic solution is injected into this outer package using a vacuum impregnation device (eg, TOSPACK V-307GII; manufactured by Todeneki Co., Ltd.), and the remaining one side is vacuum-sealed by thermocompression bonding to prepare a cell. After that, it is preferable to leave the electrode structure at rest for a predetermined time, for example, until the pores of the electrode structure are sufficiently impregnated with the injected electrolytic solution.
  • a vacuum impregnation device eg, TOSPACK V-307GII; manufactured by Todeneki Co., Ltd.
  • a wound type lithium ion secondary battery/lithium metal secondary battery (hereinafter referred to as a lithium secondary battery) has, for example, a configuration in which an electrode structure is housed in a cylindrical exterior body together with a non-aqueous electrolyte.
  • An electrode structure in a wound-type lithium secondary battery is produced by preparing a strip-shaped positive electrode, a negative electrode, and two separators, and stacking and winding them in layers. This electrode structure is accommodated in a cylindrical outer package, and an electrolytic solution is poured into the outer package and sealed to produce a wound type battery.
  • a wound-type lithium secondary battery uses a positive electrode composed of, for example, a long sheet-like positive electrode current collector and a positive electrode mixture layer containing a positive electrode active material and provided on the positive electrode current collector.
  • a negative electrode composed of a long sheet-like negative electrode current collector and a negative electrode mixture layer containing a negative electrode active material and provided on the negative electrode current collector can be used.
  • the separator is formed in a long sheet like the positive electrode and the negative electrode, and the separator is wound while being interposed between the positive electrode and the negative electrode.
  • the exterior body includes a bottomed cylindrical case body and a lid that closes the opening of the case body.
  • the lid and case body are made of metal, for example, and are insulated from each other.
  • the lid is electrically connected to the positive electrode current collector, and the case body is electrically connected to the negative electrode current collector.
  • the lid may also serve as the positive terminal, and the case body may also serve as the negative terminal.
  • Lithium secondary batteries can be charged and discharged at -10 to 80°C, for example.
  • measures such as providing a safety valve in the lid of the battery, or cutting a notch in the case body of the battery or in the gasket that is combined with this case body.
  • the lid may be provided with a current interrupting mechanism that detects the internal pressure of the battery and interrupts the current to prevent overcharging.
  • Gurley value air permeability
  • the reaction amount or adsorption amount of lithium in the polyimide porous film was measured according to the following procedure. By measuring the reaction amount of lithium to the polyimide porous film, the suitability of using the polyimide porous film as a separator of an electric storage device can be evaluated.
  • the procedure for measuring the lithium reaction amount or adsorption amount in the polyimide porous film has the following steps: (1) A step of preparing a laminate in which a porous film to be evaluated, a diaphragm, and a sheet-like lithium source are stacked in order between a pair of electrodes; (2) a step of placing the laminate in a housing and sealing an electrolytic solution in the housing to prepare an evaluation cell; calculating the amount of
  • the materials and types of the pair of electrodes 3a and 3b used in the laminate 1 are not particularly limited.
  • materials for the electrodes 3a and 3b for example, copper, aluminum, silver, zinc, or the like can be used.
  • the electrodes 3a and 3b may have any shape as long as they can hold the porous film 5, the diaphragm 7, and the lithium supply source 10 therebetween.
  • the purpose is to measure the adsorption or reaction amount of lithium in the polyimide porous film as the porous film 5, and the details of the mechanism by which lithium adsorbs to the polyimide porous film 5 are not clear. It is thought that lithium is bound or coordinated to the portion.
  • Resins with aromatic rings tend to adsorb thium, and by evaluating the amount of lithium adsorbed or reacted using this evaluation method, it is possible to determine whether the resin can be applied to lithium metal batteries that use metallic lithium as the negative electrode. You can get an estimate.
  • the lithium reaction amount is small, and the conventionally well-known polyimide porous film using BPDA/PDA has a relatively large lithium reaction amount. The initial coulombic efficiency of ion batteries and lithium metal batteries is adversely affected.
  • the polyimide porous film of the present invention reduces the reaction amount of lithium and does not deteriorate the coulombic efficiency of lithium ion batteries and lithium metal batteries.
  • the technique for making the porous film 5 to be evaluated porous there is no particular limitation on the technique for making the porous film 5 to be evaluated porous.
  • a method of obtaining the porous film 5 by preparing a slurry in which fine particles are dispersed in a polyamic acid solution, forming the slurry into a thin film, and then removing the fine particles.
  • the thickness and porosity of the porous film 5 are not particularly limited, but when comparing the reaction amount or adsorption amount of lithium for a plurality of porous films, the thickness and porosity of the porous films should be matched. In this embodiment, for example, the film thickness is adjusted to 20 ⁇ m and the porosity is 65%.
  • This porous film 5 is preferably provided on the nickel foil 13 .
  • the porous film 5 may be provided on the nickel foil by removing the fine particles, or the porous film 5 may be attached on the nickel foil 13. good.
  • the porous film 5 that has already been made porous is pasted on the nickel foil 13 , it is necessary to ensure electrical conductivity between the porous film 5 and the nickel foil 13 .
  • the diaphragm 7 is an insulating film that can prevent the pair of electrodes in the evaluation cell from coming into contact with each other, and can ensure the ionic conductivity of the electrolytic solution. It may be used as the diaphragm 7 of the cell.
  • a plate or foil 15 made of lithium may be used as the sheet-shaped lithium supply source 10 to be placed on the diaphragm 7, for example.
  • a plate or foil 17 made of lithium it is preferable to prepare a lithium metal layer 15 integrally formed on a conductor substrate 17 selected from silver, copper, or aluminum.
  • a structure is prepared by sandwiching a structure in which a porous film 5, a diaphragm 7, and a lithium supply source 10 are laminated in this order between a pair of electrodes 3a and 3b.
  • the nickel foil 13 in the porous film 5 is made to face the electrode 3a
  • the porous film 5 is made to face the diaphragm 7 .
  • the lithium supply source 10 is arranged such that a conductor substrate 17 such as copper or nickel faces the electrode 3b, and the lithium metal layer 15 faces the diaphragm 7. As shown in FIG. Thus, the laminated body 1 can be produced.
  • the laminate 1 is placed in a container, The electrolyte is injected into and sealed.
  • the container any one used for a general outer package for batteries can be used.
  • a resin laminate film for producing a laminate type battery was used as the outer packaging, but in addition to this, for example, a metal outer packaging for producing a coin battery can also be used.
  • Stainless steel or aluminum is suitable as a material for forming the exterior body for a coin battery, and it is preferable to press a stainless steel plate or an aluminum plate into a desired shape.
  • the electrolyte to be enclosed in the evaluation cell is also not limited, and may be, for example, an organic electrolyte in which a lithium salt such as LiPF 6 is dissolved in an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC). You may evaluate using LiFSI as a lithium salt.
  • a lithium salt such as LiPF 6
  • organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC).
  • the evaluation cell it is preferable to dry the evaluation cell before each member is used. Any drying method may be used as long as it does not affect the material of each member. Further, after the laminate 1 is placed in the housing, it is more preferable to dry again under conditions that do not affect all the members before pouring the liquid. It is desirable that the thickness, porosity, thickness, pore size, etc. of the porous film 5 to be evaluated be the same. For example, the type of electrode, thickness, size, size and thickness of nickel foil when the porous film has nickel foil, type and size of separator, lithium supply source, drying conditions for evaluation samples, etc. By arranging the conditions, a more rigorous evaluation becomes possible.
  • the evaluation cell is energized through the electrodes 3a and 3b. At this time, lithium is supplied from the lithium supply source 10 to the porous film 5 and reacted or adsorbed on the porous film 5 .
  • the energization step is performed at constant current and constant voltage (CCCV). For example, current is supplied at a predetermined current value such as 0.13 mA (CC). After the voltage reaches a certain value (for example, 0.01 V), the current value reaches, for example, 0.026 mA. An electric capacity is calculated by this energization step, and the amount of lithium that the polyimide porous film 5 reacts with or adsorbs can be obtained.
  • CCCV constant current and constant voltage
  • the amount of lithium reacted with or adsorbed on the polyimide porous film 5 can be measured according to the procedures (1) to (3). If the polyimide porous film 5 does not have the property of reacting with or adsorbing lithium, lithium will not react with or adsorb to the polyimide porous film 5 in the charging process, and therefore almost no current will flow in the energizing process. On the other hand, when the polyimide porous film 5 has the property of reacting with or adsorbing lithium, lithium reacts with or adsorbs to the polyimide porous film 5 in the current-applying step, so that current flows. When the polyimide porous film 5 is used as a separator for a lithium ion battery or a lithium metal battery, it is preferable that the property of reacting with or adsorbing lithium is completely absent or less.
  • Example 1 [Preparation of polyamic acid] To 16 g of N,N-dimethylacetamide, 1.915 g of 4,4'-oxydianiline and 2.086 g of pyromellitic anhydride were added, and the mixture was stirred in a separable flask at 25°C for 12 hours. It was made to react and polyamic acid was obtained. [Preparation of polyimide porous film] A slurry prepared by mixing polyamic acid and polystyrene resin particles with a particle size of 400 nm was coated on a Ni foil to make it porous. A circle having a diameter of 14 mm was punched out from a nickel foil on which a porous polyimide layer was formed, and vacuum-dried overnight.
  • the polyimide porous film layer made porous had a thickness of 20 ⁇ m and a porosity of 65%.
  • a polyolefinic film (Celgard (registered trademark) 2340) was sandwiched between PET films, punched into a circle with a diameter of 18 mm, and vacuum-dried overnight.
  • a sheet having a lithium metal layer rolled to a thickness of 20 ⁇ m on a copper foil was punched into a circle with a diameter of 16 mm.
  • a porous polyimide film, a diaphragm, and a sheet-like lithium supply source were laminated so that their respective centers were aligned, and sandwiched between a pair of electrodes to produce a laminate.
  • a disk-shaped copper plate with a diameter of 16 mm was used as the electrode.
  • the nickel foil was opposed to the electrode, and the porous polyimide layer was opposed to the diaphragm.
  • the lithium metal layer was opposed to the diaphragm and the copper foil was opposed to the electrode.
  • Example 2 In the same manner as in Example 1 except that 0.581 g of p-phenylenediamine and 1.076 g of 4,4'-oxydianiline were used as diamines, and 2.343 g of pyromellitic anhydride was used as carboxylic acid. Li reaction amount was measured. It should be noted that the polyamic acid shown in any of the examples and comparative examples could be used to form a film and make it porous.
  • Example 3 In the same manner as in Example 1 except that 0.332 g of p-phenylenediamine and 1.435 g of 4,4'-oxydianiline were used as diamines, and 2.233 g of pyromellitic anhydride was used as carboxylic acid. Li reaction amount was measured. It should be noted that the polyamic acid shown in any of the examples and comparative examples could be used to form a film and make it porous.
  • Example 4 In the same manner as in Example 1 except that 0.106 g of p-phenylenediamine and 1.762 g of 4,4'-oxydianiline were used as diamines, and 2.132 g of pyromellitic anhydride was used as carboxylic acid. Li reaction amount was measured. It should be noted that the polyamic acid shown in any of the examples and comparative examples could be used to form a film and make it porous.
  • Example 5 The reaction amount of Li was measured in the same manner as in Example 1 except that 1.973 g of 2,2'-dimethylbenzidine was used as the diamine and 2.027 g of pyromellitic anhydride was used as the carboxylic acid.
  • Example 7 0.527 g of p-phenylenediamine and 0.976 g of 4,4'-oxydianiline were used as diamines, and 1.063 g of pyromellitic anhydride and 3,3',4,4'-biphenyl were used as carboxylic acids.
  • the reaction amount of Li was measured in the same manner as in Example 1 except that 1.434 g of tetracarboxylic dianhydride was used.
  • Example 8 Example 1 except that 0.176 g of p-phenylenediamine and 1.302 g of 4,4'-oxydianiline were used as diamines, and 2.522 g of 4,4'-oxydiphthalic anhydride was used as carboxylic acid. Li reaction amount was measured in the same manner as above.
  • Example 9 0.454 g of p-phenylenediamine and 0.841 g of 4,4'-diaminodiphenyl ether were used as the diamine, and 2.705 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride was used as the carboxylic acid.
  • the reaction amount of Li was measured in the same manner as in Example 1, except that it was used.
  • Example 10 Same as Example 1 except that 2,2'-dimethylbenzidine: 1.677 g was used as the diamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride: 2.324 g was used as the carboxylic acid. Then, the Li reaction amount was measured.
  • Comparative example 1 Li The reaction volume was measured.
  • a raw film was produced based on a slurry prepared with reference to the polyamic acids listed in Table 1, and this raw film was baked to produce a polyimide porous film.
  • Polystyrene resin particles having a particle size of 400 nm were used as the fine particles. Details are given below.
  • Example S1 [Preparation of polyamic acid] 1.9729 g of 2,2′-dimethylbenzidine and 2.0271 g of pyromellitic anhydride were added to 16 g of N,N-dimethylacetamide, and the mixture was stirred in a separable flask at 25° C. for 12 hours to react. , to obtain polyamic acid. A slurry was prepared by adding 5.4930 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die.
  • the unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film.
  • the porosity was approximately 65% and the film thickness was 20 ⁇ m.
  • the Gurley value was 86.1 seconds, and the Li reaction amount was 70 mAh/g.
  • Table 2 The physical properties are summarized in Table 2. Examples S2 to S6 and Comparative Examples C1 and C2, which will be described later, are also summarized in Table 2.
  • a slurry was prepared by adding 6.225 g of polymethyl methacrylate particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged onto a support from a T-die to produce a raw roll. Polymethyl methacrylate particles were removed by heat treatment to produce a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 ⁇ m, the Gurley value was 89.4 seconds, and the Li reaction amount was 55 mAh/g.
  • a slurry was prepared by adding 6.225 g of polymethyl methacrylate particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged onto a support from a T-die to produce a raw roll. Polymethyl methacrylate particles were removed by heat treatment to produce a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 ⁇ m, the Gurley value was 100 seconds, and the Li reaction amount was 330 mAh/g.
  • Example S4 N,N-dimethylacetamide: 16 g, 3,3′,4,4′-biphenyltetracarboxylic dianhydride: 1.728 g, pyromellitic anhydride: 0.854 g, p-phenylenediamine: 0.635 g, and 4,4′-oxydianiline: 0.784 g were added and stirred in a separable flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
  • a slurry was prepared by adding 5.493 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die.
  • the unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film.
  • the porosity was approximately 65% and the film thickness was 20 ⁇ m.
  • Example S5 N,N-dimethylacetamide: 16 g, 3,3′,4,4′-biphenyltetracarboxylic dianhydride: 1.434 g, pyromellitic anhydride: 1.063 g, p-phenylenediamine: 0.527 g, and 4,4′-oxydianiline: 0.976 g were added and stirred in a separable flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
  • a slurry was prepared by adding 5.493 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die.
  • the unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film.
  • the porosity was about 65%
  • the film thickness was 20 ⁇ m
  • the Gurley value was 100 seconds
  • the Li reaction amount was 199 mAh/g.
  • Example S6 N,N-dimethylacetamide: 16 g, 3,3',4,4'-biphenyltetracarboxylic dianhydride: 1.143 g, pyromellitic anhydride: 1.271 g, p-phenylenediamine: 0.420 g, and 4,4′-oxydianiline: 1.167 g were added and stirred in a separable flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
  • a slurry was prepared by adding 5.493 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die. The unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film.
  • the porosity was approximately 65% and the film thickness was 20 ⁇ m.
  • Comparative example C1 2.9249 g of 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 1.0751 g of p-phenylenediamine were added to 16 g of N,N-dimethylacetamide, and the mixture was placed in a separable flask for 25 minutes. C. for 12 hours and reacted to obtain a polyamic acid.
  • a slurry was prepared by adding 5.4930 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and the slurry was discharged from a T-die onto a support, and the particles were removed by heat treatment to prepare a polyimide porous film.
  • the porosity was approximately 65%
  • the film thickness was 20 ⁇ m
  • the Gurley value was 100 seconds
  • the Li reaction amount was 1275 mAh/g.
  • Comparative example C2 1.9145 g of 4,4'-oxydianiline and 2.0855 g of pyromellitic anhydride were added to 16 g of N,N-dimethylacetamide, and the mixture was stirred in a separable flask at 25°C for 12 hours to react. to obtain polyamic acid.
  • a slurry was prepared by adding 6.1207 g of polymethyl methacrylate particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged onto a support from a T-die to produce a raw roll. Polymethyl methacrylate particles were removed by heat treatment to produce a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 ⁇ m, the Gurley value was 64.1 seconds, and the Li reaction amount was 73 mAh/g.

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Abstract

The purpose of the present invention is to provide a polyimide porous film that is suitable as a separator of a power storage device such as a lithium ion battery or a lithium metal battery. A polyimide porous film according to the present invention can be used as a separator for a battery. The polyimide porous film composed of a copolymer of carboxylic acid and diamine and having a plurality of pores formed therein is characterized in that dimethylbenzidine is contained as the diamine. It is desirable that the carboxylic acid include at least one among a pyromellitic dianhydride and a biphenyltetracarboxylic dianhydride. Moreover, the pore diameter of the pores of the polyimide porous film is at most 800 nanometers.

Description

ポリイミド多孔質フィルム、電極構造体および蓄電デバイスPolyimide porous film, electrode structure and power storage device
　本発明は、ポリイミド多孔質フィルム、電極構造体、および蓄電デバイスに関する。 The present invention relates to polyimide porous films, electrode structures, and electricity storage devices.
　近年、リチウムイオン電池やキャパシタなどの蓄電デバイスが普及している。中でも黒鉛を負極とするリチウムイオン電池、リチウムイオンキャパシタ、金属リチウムを負極とするリチウム金属電池などの技術が著しく発展している。これら蓄電デバイスは、正極、セパレータ、負極が順に積層配置され電解液が満たされ、セパレータによって正極と負極とが絶縁された構造を有しており、これらの負極としては、例えば金属リチウム、リチウムと他の金属との合金、カ－ボンやグラファイト等がよく用いられる。 In recent years, power storage devices such as lithium-ion batteries and capacitors have become widespread. Among them, technologies such as lithium ion batteries and lithium ion capacitors using graphite as a negative electrode and lithium metal batteries using metallic lithium as a negative electrode have been remarkably developed. These electric storage devices have a structure in which a positive electrode, a separator, and a negative electrode are stacked in order and filled with an electrolytic solution, and the positive electrode and the negative electrode are insulated by the separator. Alloys with other metals, carbon and graphite are often used.
　近年、耐熱性の比較的高いポリイミド材料で構成した多孔質膜を絶縁用のセパレータとして用いることが検討されている（特許文献１）。 In recent years, the use of a porous film made of a polyimide material with relatively high heat resistance as an insulating separator has been studied (Patent Document 1).
特開２０１６－１８３２７３号公報JP 2016-183273 A
　ところで特許文献１に記載されるようなポリイミド多孔質フィルムは蓄電デバイス用のセパレータとして用いることができるが、ポリイミド多孔質フィルムをセパレータとして組み込んだ蓄電デバイスの更なる高性能化が求められている。 By the way, a polyimide porous film as described in Patent Document 1 can be used as a separator for an electricity storage device, but there is a demand for higher performance of an electricity storage device incorporating a polyimide porous film as a separator.
　本発明は、リチウムイオン電池やリチウム金属電池など蓄電デバイスおよびこれに用いる電極構造体のセパレータとして好適なポリイミド多孔質フィルムを提供することを第１の目的とするものである。
　この第１の目的に鑑み、本発明者らは鋭意検討し、ポリイミド多孔質フィルムを形成するためのポリアミック酸を適切なカルボン酸およびジアミンから生成することで、リチウムイオン電池やリチウム金属電池などの蓄電デバイスにおける初期の充放電特性を改善できることを見出した。 A first object of the present invention is to provide a polyimide porous film suitable as a separator for an electric storage device such as a lithium ion battery or a lithium metal battery and an electrode structure used therein.
In view of this first object, the present inventors have made intensive studies, and produced polyamic acid for forming a polyimide porous film from an appropriate carboxylic acid and diamine, thereby producing lithium ion batteries, lithium metal batteries, and the like. We have found that the initial charge/discharge characteristics of an electricity storage device can be improved.
　また、本発明は、電極構造体用や、蓄電デバイス用に限らず、バランスよく膜強度に優れたポリイミド多孔質フィルムを提供することを第２の目的とするものである。特に第１の発明に依存することなくある程度の膜強度を保持することができる。 A second object of the present invention is to provide a polyimide porous film that is well-balanced and excellent in film strength, not only for use in electrode structures and electricity storage devices. In particular, a certain degree of film strength can be maintained without depending on the first invention.
　上述した第１の目的を達成するために、第１の発明であるポリイミド多孔質フィルムは以下の［１］～［５］の構成を有する。 In order to achieve the first object described above, the polyimide porous film of the first invention has the following configurations [1] to [5].
［１］
　カルボン酸とジアミンとの共重合体で構成され、多数の細孔が形成されたポリイミド多孔質フィルムであって、ジアミンとして、ジメチルベンジジンを含有することを特徴とする。
　ジメチルベンジジンとしては、２，２’－ジメチルベンジジンおよび３，３’－ジメチルベンジジンがあり、このうち、２，２’－ジメチルベンジジンが好ましい。本発明のポリイミド多孔質フィルムはリチウム反応量を低減しており、リチウムイオン電池やリチウム金属電池に本発明のポリイミド多孔質フィルムを用いる場合、クーロン効率の悪化を抑えることができる。 [1]
A polyimide porous film comprising a copolymer of a carboxylic acid and a diamine, having a large number of pores, and containing dimethylbenzidine as the diamine.
Dimethylbenzidine includes 2,2'-dimethylbenzidine and 3,3'-dimethylbenzidine, of which 2,2'-dimethylbenzidine is preferred. The polyimide porous film of the present invention reduces the amount of reaction with lithium, and when the polyimide porous film of the present invention is used in a lithium ion battery or a lithium metal battery, deterioration of coulombic efficiency can be suppressed.
［２］
　カルボン酸としてピロメリット酸二無水物およびビフェニルテトラカルボン酸二無水物の少なくともどちらか一方を含むことを特徴とする。ピロメリット酸二無水物およびビフェニルテトラカルボン酸二無水物の両方をブレンドしてもちいてもよいが、ジメチルベンジジンをピロメリット酸と組み合わせることで、ポリイミド多孔質フィルムの強度を改善することができる。 [2]
It is characterized by containing at least one of pyromellitic dianhydride and biphenyltetracarboxylic dianhydride as carboxylic acid. Although both pyromellitic dianhydride and biphenyltetracarboxylic dianhydride may be blended and used, the strength of the polyimide porous film can be improved by combining dimethylbenzidine with pyromellitic acid.
［３］
　また、本発明のポリイミド多孔質フィルムの細孔の孔径は８００ナノメートル以下であることが望ましい。細孔の孔径は小さい方が好ましく、７００ｎｍ以下がより好ましく、６００ｎｍ以下が更に好ましいが、この細孔径はポリイミド多孔質フィルムの用途に鑑みて定めるとよい。 [3]
Moreover, the pore size of the pores of the polyimide porous film of the present invention is preferably 800 nanometers or less. The pore diameter of the pores is preferably as small as possible, more preferably 700 nm or less, and even more preferably 600 nm or less.
［４］
　本発明のポリイミド多孔質フィルムの最大応力は２５Ｎ／ｍｍ２以上である。この最大応力の測定方法ないし条件は後述するとおりである。 [4]
The maximum stress of the polyimide porous film of the present invention is 25 N/mm 2 or more. The method and conditions for measuring this maximum stress are as described later.
［５］
　本発明のポリイミド多孔質フィルムの破断エネルギーは０．３４Ｊ／ｍｍ以上である。
　破断エネルギーの測定方法および条件も後述する。
　本発明によって従来は困難であった、最大応力が２５Ｎ／ｍｍ２以上であって、かつ破断エネルギーが０．３４Ｊ／ｍｍ以上であるポリイミド多孔質フィルムを提供することが可能となる。
　なお、上記［１］～［５］のポリイミド多孔質フィルムをセパレータとして用いた蓄電デバイス、特にリチウムイオン電池やリチウム金属電池では、初期の充放電においてリチウムがポリイミド多孔質フィルムに反応ないし吸着することを低減でき、初期の充放電特性を改善することができる。 [5]
The breaking energy of the polyimide porous film of the present invention is 0.34 J/mm or more.
The method and conditions for measuring the breaking energy will also be described later.
The present invention makes it possible to provide a polyimide porous film having a maximum stress of 25 N/mm 2 or more and a breaking energy of 0.34 J/mm or more, which was conventionally difficult.
In addition, in an electricity storage device using the polyimide porous film of [1] to [5] as a separator, especially in a lithium ion battery or a lithium metal battery, lithium reacts or adsorbs to the polyimide porous film during initial charging and discharging. can be reduced, and the initial charge/discharge characteristics can be improved.
　また、本発明の第２の目的を達成するために本発明のポリイミド多孔質フィルムは以下の構成を有する：
　ビフェニルテトラカルボン酸二無水物およびピロメリット酸二無水物の両方を含むカルボン酸と、パラフェニレンジアミンおよびオキシジアニリンの両方を含むジアミンとの共重合体で構成されることを特徴とする。 Also, in order to achieve the second object of the present invention, the polyimide porous film of the present invention has the following configuration:
It is characterized by comprising a copolymer of a carboxylic acid containing both biphenyltetracarboxylic dianhydride and pyromellitic dianhydride and a diamine containing both paraphenylenediamine and oxydianiline.
　ビフェニルテトラカルボン酸二無水物およびピロメリット酸二無水物の比率はモル比で１：１が好ましいが、この比率は多少前後してもよく４：６～６：４の範囲で定めるとよい。
　また、パラフェニレンジアミンおよびオキシジアニリンの比率もモル比で１：１が好ましいが、この比率も４：６～６：４で定めるとよい。
　ジアミンとしてジメチルベンジジンを組み合わせて用いても良い。
　後述するが、このような比率で混合することで最大応力、弾性率、伸び、破断エネルギーなどを両立させることが可能なポリイミド多孔膜を提供することが可能となる。 The molar ratio of biphenyltetracarboxylic dianhydride and pyromellitic dianhydride is preferably 1:1, but this ratio may vary slightly and is preferably set in the range of 4:6 to 6:4.
Also, the molar ratio of p-phenylenediamine and oxydianiline is preferably 1:1, but this ratio is also preferably 4:6 to 6:4.
As a diamine, dimethylbenzidine may be used in combination.
As will be described later, by mixing in such a ratio, it is possible to provide a polyimide porous membrane that can satisfy both the maximum stress, elastic modulus, elongation, breaking energy, and the like.
　本発明のポリイミド多孔質フィルムに形成された無数の細孔は、ポリアミック酸を含むスラリーに予め混合された微粒子を焼成時に除去することで形成することができる。 The countless pores formed in the polyimide porous film of the present invention can be formed by removing fine particles previously mixed in a slurry containing polyamic acid during firing.
　本発明のカルボン酸およびジアミンから形成されたポリアミック酸を用いたポリイミド多孔質フィルムは、従来のもの、特にカルボン酸としてビフェニルテトラカルボン酸を用いたポリイミド多孔質フィルムと比較して、リチウムと反応ないし吸着する量を低減することができる。
　これにより蓄電デバイスの充放電初期において、セパレータであるポリイミド多孔質フィルムと反応ないし吸着するリチウムの量を低減でき、初期の充放電の挙動を良好なものにすることができる。 The polyimide porous film using a polyamic acid formed from a carboxylic acid and a diamine of the present invention reacts or reacts with lithium as compared with a conventional polyimide porous film, especially a polyimide porous film using biphenyltetracarboxylic acid as a carboxylic acid. The amount to be adsorbed can be reduced.
As a result, the amount of lithium that reacts with or adsorbs to the polyimide porous film, which is the separator, can be reduced in the early stages of charging and discharging of the electrical storage device, and the initial charging and discharging behavior can be improved.
ポリイミド多孔質フィルムと反応ないし吸着するリチウムの量を測定するために作製される積層体を、当該ポリイミド多孔質フィルムと略垂直な平面で切断した断面図である。FIG. 2 is a cross-sectional view of a laminate produced for measuring the amount of lithium that reacts with or adsorbs to a polyimide porous film, cut along a plane substantially perpendicular to the polyimide porous film.
　以下に、本発明のポリイミド多孔質フィルムについて説明する。本発明の、カルボン酸とジアミンとの共重合体で構成されたポリイミド多孔質フィルムはリチウムイオン電池やリチウム金属電池あるいはキャパシタなどの蓄電デバイス用のセパレータとして用いてもよいし、その他の用途に用いてもよく、用途に制限はない。 The polyimide porous film of the present invention will be described below. The polyimide porous film of the present invention composed of a copolymer of carboxylic acid and diamine may be used as a separator for an electric storage device such as a lithium ion battery, a lithium metal battery, or a capacitor, or may be used for other purposes. There is no limit to the usage.
　本発明のポリイミド多孔質フィルムを蓄電デバイス用のセパレータとして用いる場合は、重量法による空孔率が４５～７５％であることが好ましく、ガーレ値（透気度）は３００秒以下が好ましい。空孔率４５％以上であれば、例えば膜厚２０μｍでガーレ値を３００秒/１００ｃｃ以下にでき、後述するＬｉ反応量の観点だけでなく、ガーレ値の観点からも好ましいセパレータを提供することができる。
　空孔率を高くするとガーレ値を小さくできるが、例えば空孔率７０％超など空孔率を高めるほどポリイミド多孔質フィルムの膜強度が弱まる。このため、実際の電池製造の際に当該フィルムが損傷してしまうことがあるため、空孔率を８０％以上などに高めたポリイミド多孔質フィルムで電池を組み上げることは難しい。 When the polyimide porous film of the present invention is used as a separator for an electric storage device, the porosity by weight method is preferably 45 to 75%, and the Gurley value (air permeability) is preferably 300 seconds or less. If the porosity is 45% or more, the Gurley value can be 300 seconds/100cc or less at a film thickness of 20 μm, for example, and it is possible to provide a separator that is preferable not only from the viewpoint of the Li reaction amount described later but also from the viewpoint of the Gurley value. can.
Although the Gurley value can be reduced by increasing the porosity, the film strength of the polyimide porous film is weakened as the porosity is increased, for example, the porosity exceeds 70%. For this reason, the film may be damaged during actual battery production, and it is difficult to assemble a battery using a polyimide porous film with an increased porosity of 80% or more.
　ポリイミド多孔質フィルムの厚みは、例えば４μｍ～５０μｍ程度が好ましい。ポリイミド多孔質フィルムの厚みが厚すぎるとイオン伝導性が低下する傾向が見られる。また短絡耐性にも関係しており、膜厚を薄くするほど、絶縁性が維持できなくなる傾向がある。またポリイミド多孔質フィルムが薄すぎると、膜強度が低下する。また、ポリイミド多孔質フィルムの最大応力は２５Ｎ／ｍｍ２以上であることが好ましい。 The thickness of the polyimide porous film is preferably, for example, about 4 μm to 50 μm. If the thickness of the polyimide porous film is too thick, there is a tendency for the ionic conductivity to decrease. It is also related to short-circuit resistance, and there is a tendency that the thinner the film, the more difficult it becomes to maintain the insulation. On the other hand, if the polyimide porous film is too thin, the film strength will decrease. Also, the maximum stress of the polyimide porous film is preferably 25 N/mm 2 or more.
　本発明のポリイミド多孔質フィルムの製造では、例えば、ポリアミック酸を化学イミド化または加熱によってイミド化させる方法など、公知の手法を用いることができ、以下の工程で作製することができる：
　カルボン酸無水物と有機アミン化合物とからポリアミック酸（いわゆるポリイミドワニス）を含有したポリイミド前駆体溶液に開孔用の微粒子を混ぜてスラリーを作製する工程、
　作製されたスラリーを支持体上に薄膜状に形成し無孔の原反を形成する工程、
　当該原反を支持体から剥離する工程、
　当該原反を焼成して多孔化する工程。
　なお、開孔用の微粒子の除去と原反のイミド化は同時並行的に実施することもできるが、原反から微粒子を除去して開孔化したのちにイミド化することもできる。 In the production of the polyimide porous film of the present invention, for example, a known technique such as chemical imidization or heat imidation of polyamic acid can be used, and the film can be produced by the following steps:
A step of mixing fine particles for opening holes into a polyimide precursor solution containing polyamic acid (so-called polyimide varnish) from a carboxylic acid anhydride and an organic amine compound to prepare a slurry;
a step of forming the prepared slurry into a thin film on a support to form a non-porous raw fabric;
A step of peeling the raw fabric from the support,
A step of firing the original fabric to make it porous.
The removal of fine particles for forming pores and the imidization of the raw fabric can be carried out in parallel, but it is also possible to remove the fine particles from the raw fabric, open the pores, and then imidize the raw fabric.
　［スラリー作製］
　ポリイミド前駆体溶液は、カルボン酸無水物と有機アミン化合物とから作製されるポリアミック酸を含む。ポリアミック酸、もしくはポリアミック酸と溶媒との混合物をポリイミド前駆体溶液とし、これに開口用の微粒子を混合することでスラリーを作製することができる。なお、ポリイミド前駆体溶液は、有機溶媒の存在下でテトラカルボン酸二無水物とジアミンとを重合反応させて得られる溶液であってもよいが、ポリアミック酸を有機溶媒に溶解させて得られる溶液でもどちらでもかまわない。 [Slurry preparation]
A polyimide precursor solution includes a polyamic acid made from a carboxylic anhydride and an organic amine compound. A polyamic acid or a mixture of a polyamic acid and a solvent is used as a polyimide precursor solution, and fine particles for opening are mixed into the polyimide precursor solution to prepare a slurry. The polyimide precursor solution may be a solution obtained by polymerizing a tetracarboxylic dianhydride and a diamine in the presence of an organic solvent, or a solution obtained by dissolving a polyamic acid in an organic solvent. But it doesn't matter which.
　ポリイミド前駆体溶液、開孔用の微粒子のほか、分散剤や溶剤などを混合して成膜用のスラリーを作製する。このスラリーを薄膜状に成形することで無孔の原反を作製することができる。分散剤は必須ではなく、必要に応じ適宜用いるとよい。
　開孔用の微粒子の材質は、ポリイミド前駆体溶液に使用する有機溶剤に不溶で、成膜後に選択的に除去可能なものであればよい。
　例えば、無機材料で構成される微粒子としては、シリカ（二酸化珪素）、酸化チタン、アルミナ（Ａｌ２Ｏ３）等の金属酸化物などがあげられる。
　有機材料で構成される微粒子としては、ポリプロピレンやポリエチレン等のポリオレフィン、ポリスチレン（ＰＳ）、アクリル系樹脂（例えばメタクリル酸メチル、メタクリル酸イソブチル、ポリメチルメタクリレート（ＰＭＭＡ）等）、ポリウレタン樹脂（ＰＵＲ）、メラミン樹脂（ＭＦ）、ユリア樹脂（ＵＦ）、フェノール樹脂（ＰＦ）、エポキシ樹脂、セルロース、ポリビニルアルコール、ポリビニルブチラール、ポリ酢酸ビニル(ＰＶＡｃ)、ＡＢＳ樹脂、ＡＳ樹脂、ポリアクリロニトリル（ＰＡＮ）、ポリカーボネート（ＰＣ）、ポリアミド（ＰＡ）、ポリエチレンテレフタラート（ＰＥＴ）、ポリエステル、ポリエーテル等の有機高分子で構成された微粒子（以降、樹脂微粒子という）が挙げられる。 A slurry for forming a film is prepared by mixing a polyimide precursor solution, fine particles for opening holes, a dispersant, a solvent, and the like. By forming this slurry into a thin film, a non-porous raw fabric can be produced. A dispersant is not essential, and may be used as appropriate.
The material of the fine particles for opening holes may be any material as long as it is insoluble in the organic solvent used for the polyimide precursor solution and can be selectively removed after film formation.
For example, fine particles composed of an inorganic material include metal oxides such as silica (silicon dioxide), titanium oxide, and alumina (Al2O3).
Fine particles composed of organic materials include polyolefins such as polypropylene and polyethylene, polystyrene (PS), acrylic resins (e.g., methyl methacrylate, isobutyl methacrylate, polymethyl methacrylate (PMMA), etc.), polyurethane resins (PUR), Melamine resin (MF), urea resin (UF), phenol resin (PF), epoxy resin, cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetate (PVAc), ABS resin, AS resin, polyacrylonitrile (PAN), polycarbonate ( (PC), polyamide (PA), polyethylene terephthalate (PET), polyester, polyether, and other organic polymers (hereinafter referred to as resin fine particles).
　微粒子の形状に制限はないが、球状または略球状が望ましい。基本的に真球に近い形状が望ましいが、多少の歪みや細かい凹凸等を有する、楕円形状など略球状の形状であってもかまわない。
　また真球形状に近く粒径分布指数の小さい（粒径のばらつきの小さい）微粒子が好ましい。これらの条件を有する微粒子を用いることでポリイミド多孔質フィルムに形成される細孔孔径のばらつきを小さくすることができる。
　これによりポリイミド多孔質フィルムを蓄電デバイスのセパレータとして使用した場合に、リチウムをセパレータ上でより均一に移動させることができるようになる。微粒子の粒径としては、８００ｎｍ以下のものを用いるとよい。これにより、微粒子を取り除いて得られる多孔質フィルムの開孔径を８００ｎｍ以下にすることができる。より好ましい微粒子の粒径は、６００ｎｍ以下、さらに好ましくは５００ｎｍ以下である。 Although the shape of the fine particles is not limited, spherical or approximately spherical shapes are desirable. Basically, a shape close to a true sphere is desirable, but a substantially spherical shape such as an ellipse having some distortion, fine irregularities, etc. may also be used.
Further, fine particles having a nearly spherical shape and a small particle size distribution index (small variation in particle size) are preferable. By using fine particles satisfying these conditions, it is possible to reduce the variation in pore size formed in the polyimide porous film.
As a result, when the polyimide porous film is used as a separator of an electric storage device, lithium can be moved more uniformly on the separator. As for the particle size of the fine particles, it is preferable to use those having a particle size of 800 nm or less. Thereby, the pore diameter of the porous film obtained by removing the fine particles can be made 800 nm or less. More preferably, the particle size of the fine particles is 600 nm or less, more preferably 500 nm or less.
　ポリイミド前駆体溶液中で微粒子を均一に分散することを目的に、ポリイミド前駆体溶液中に分散剤を添加してもよい。分散剤を添加することにより、ポリアミック酸と微粒子とをより均一に混合することができ、後述する原反において微粒子をより均一に分布させることができる。微粒子を均一に分布させることで、最終的に微粒子を除去して得られるポリイミド多孔質フィルムにおいて、細孔の分布をより均一にすることができる。 A dispersant may be added to the polyimide precursor solution for the purpose of uniformly dispersing the fine particles in the polyimide precursor solution. By adding a dispersant, the polyamic acid and the fine particles can be mixed more uniformly, and the fine particles can be more uniformly distributed in the raw fabric described later. By uniformly distributing the fine particles, the polyimide porous film obtained by finally removing the fine particles can have a more uniform pore distribution.
　＜カルボン酸無水物およびポリアミック酸＞
　ポリアミック酸としては、カルボン酸二無水物とジアミンとを重合して得られるものを使用することができる。カルボン酸二無水物およびジアミンの使用量も特に制限はないが、カルボン酸二無水物１モルに対して、ジアミンを０．５０～１．５０モルが好ましく、０．６０～１．３０モルがより好ましく、０．７０～１．２０モルが特に好ましい。
　カルボン酸二無水物は、従来からポリアミック酸の合成原料として使用されているものの中から適切に選択するとよい。カルボン酸二無水物は、芳香族テトラカルボン酸二無水物であっても、脂肪族テトラカルボン酸二無水物であってもよいが、得られるポリイミド樹脂の耐熱性の点から、芳香族テトラカルボン酸二無水物を使用することが好ましい。カルボン酸二無水物は、２種以上を組合せて用いてもよい。 <Carboxylic anhydride and polyamic acid>
As the polyamic acid, those obtained by polymerizing a carboxylic acid dianhydride and a diamine can be used. The amount of the carboxylic acid dianhydride and the diamine to be used is not particularly limited, but the diamine is preferably 0.50 to 1.50 mol, and 0.60 to 1.30 mol, per 1 mol of the carboxylic dianhydride. More preferably, 0.70 to 1.20 mol is particularly preferred.
The carboxylic acid dianhydride may be appropriately selected from those conventionally used as raw materials for synthesizing polyamic acids. The carboxylic dianhydride may be either an aromatic tetracarboxylic dianhydride or an aliphatic tetracarboxylic dianhydride. Preference is given to using dianhydrides. Two or more carboxylic acid dianhydrides may be used in combination.
　芳香族テトラカルボン酸二無水物の好適な具体例としては、ピロメリット酸二無水物、１，１－ビス（２，３－ジカルボキシフェニル）エタン二無水物、３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物、ビス（２，３－ジカルボキシフェニル）メタン二無水物、ビス（３，４－ジカルボキシフェニル）メタン二無水物、２，２－ビス（３，４－ジカルボキシフェニル）プロパン二無水物、２，２－ビス（２，３－ジカルボキシフェニル）プロパン二無水物、２，２－ビス（３，４－ジカルボキシフェニル）－１，１，１，３，３，３－へキサフルオロプロパン二無水物、２，２－ビス（２，３－ジカルボキシフェニル）－１，１，１，３，３，３－ヘキサフルオロプロパン二無水物、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物、ビス（３，４－ジカルボキシフェニル）エーテル二無水物、ビス（２，３－ジカルボキシフェニル）エーテル二無水物、ベンゾフェノンテトラカルボン酸二無水物、１，２，５，６－ナフタレンテトラカルボン二無水物、１，４，５，８－ナフタレンテトラカルボン酸二無水物、２，３，６，７－ナフタレンテトラカルボン酸二無水物、１，２，３，４－ベンゼンテトラカルボン酸二無水物、ジフタル酸二無水物、３，４，９，１０－ペリレンテトラカルボン酸二無水物、２，３，６，７－アントラセンテトラカルボン酸二無水物、１，２，７，８－フェナントレンテトラカルボン酸二無水物、９，９－ビス(３，４－ジカルボキシフェニル)フルオレン二無水物、３，３’，４，４’－ジフェニルスルホンテトラカルボン酸二無水物等が挙げられる。
　脂肪族テトラカルボン酸二無水物としては、例えば、エチレンテトラカルボン酸二無水物、ブタンテトラカルボン酸二無水物、シクロペンタンテトラカルボン酸二無水物、シクロへキサンテトラカルボン酸二無水物、１，２，４，５－シクロへキサンテトラカルボン酸二無水物、１，２，３，４－シクロヘキサンテトラカルボン酸二無水物等が挙げられる。カルボン酸二無水物としてピロメリット酸二無水物およびビフェニルテトラカルボン酸二無水物の少なくともどちらか一方を含むことが特に好ましい。
　これらのテトラカルボン酸二無水物は、単独あるいは二種以上混合して用いることもできる。 Preferred specific examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 3,3′,4,4 '-biphenyltetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4- Dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3 ,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3 ',4,4'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, benzophenonetetracarboxylic dianhydride anhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, diphthalic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 3,3',4,4'-diphenyl sulfonetetracarboxylic dianhydride and the like.
Examples of aliphatic tetracarboxylic dianhydrides include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 1, 2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride and the like. It is particularly preferable to include at least one of pyromellitic dianhydride and biphenyltetracarboxylic dianhydride as the carboxylic dianhydride.
These tetracarboxylic dianhydrides can be used alone or in combination of two or more.
　＜有機アミン化合物＞
　有機アミン化合物であるジアミンは、従来からポリアミック酸の合成原料として使用されているジアミンから適宜選択するとよい。ジアミンは、芳香族ジアミンであっても、脂肪族ジアミンであってもよく、目的とするポリイミド樹脂の特性に鑑み、適宜選択することができるが、芳香族ジアミンが好ましい。またジアミンは２種以上を組合せて用いてもよい。 <Organic amine compound>
The diamine, which is an organic amine compound, may be appropriately selected from diamines conventionally used as raw materials for synthesizing polyamic acids. The diamine may be either an aromatic diamine or an aliphatic diamine, and can be appropriately selected in view of the properties of the intended polyimide resin, but the aromatic diamine is preferred. Moreover, you may use a diamine in combination of 2 or more types.
　芳香族ジアミンとしては、フェニレンジアミンおよびその誘導体、ジアミノビフェニル化合物およびその誘導体、ジアミノジフェニル化合物およびその誘導体、ジアミノトリフェニル化合物およびその誘導体、ジアミノナフタレンおよびその誘導体、アミノフェニルアミノインダンおよびその誘導体、ジアミノテトラフェニル化合物およびその誘導体、ジアミノヘキサフェニル化合物およびその誘導体、カルド型フルオレンジアミン誘導体などを挙げることができる。 Examples of aromatic diamines include phenylenediamine and its derivatives, diaminobiphenyl compounds and their derivatives, diaminodiphenyl compounds and their derivatives, diaminotriphenyl compounds and their derivatives, diaminonaphthalene and its derivatives, aminophenylaminoindane and its derivatives, diaminotetra Examples include phenyl compounds and derivatives thereof, diaminohexaphenyl compounds and derivatives thereof, cardo-type fluorenediamine derivatives and the like.
　ベンゼン核の数に基づいてジアミンの具体例を挙げると以下の１）～３）である：
１）ベンゼン核１つのべンゼンジアミン
２，４－ジアミノトルエン、フェニレンジアミン、２，６－ジアミノトルエンなど。 Specific examples of diamines based on the number of benzene nuclei are the following 1) to 3):
1) Benzenediamine having one benzene nucleus, such as 2,4-diaminotoluene, phenylenediamine, and 2,6-diaminotoluene.
２）ベンゼン核２つのジアミン
３，３’－ジメチル－４，４’－ジアミノビフェニル、２，２’－ジメチル－４，４’－ジアミノビフェニル、２，２’－ビス（トリフルオロメチル）－４，４’－ジアミノビフェニル、３，３’－ジメチル－４，４’－ジアミノジフェニルメタン、３，３’－ジカルボキシ－４，４’－ジアミノジフェニルメタン、３，３’，５，５’－テトラメチル－４，４’－ジアミノジフェニルメタン、ビス（４－アミノフェニル）スルフィド、４，４’－ジアミノベンズアニリド、ジメチルベンジジン、３，３’－ジメトキシベンジジン、２，２’－ジメトキシベンジジン、３，３’－ジアミノジフェニルエーテル、３，４’－ジアミノジフェニルエーテル、４，４’－ジアミノジフェニルエーテル、３，３’－ジアミノジフェニルスルフィド、オキシジアニリン、３，４’－ジアミノジフェニルスルフィド、４，４’－ジアミノジフェニルスルフィド、３，３’－ジアミノジフェニルスルホン、３，４’－ジアミノジフェニルスルホン、４，４’－ジアミノジフェニルスルホン、３，３’－ジアミノベンゾフェノン、３，３’－ジアミノ－４，４’－ジクロロベンゾフェノン、３，３’－ジアミノ－４，４’－ジメトキシベンゾフェノン、３，３’－ジアミノジフェニルメタン、３，４’－ジアミノジフェニルメタン、４，４’－ジアミノジフェニルメタン、２，２－ビス（３－アミノフェニル）プロパン、２，２－ビス（４－アミノフェニル）プロパン、２，２－ビス（３－アミノフェニル）－１，１，１，３，３，３－ヘキサフルオロプロパン、２，２－ビス（４－アミノフェニル）－１，１，１，３，３，３－ヘキサフルオロプロパン、３，３’－ジアミノジフェニルスルホキシド、３，４’－ジアミノジフェニルスルホキシド、４，４‘－ジアミノ－３, ３’－ジメチルジフェニルメタン、４，４’－ジアミノジフェニルスルホキシドなど。 2) diamines with two benzene nuclei 3,3′-dimethyl-4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-bis(trifluoromethyl)-4 ,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl -4,4'-diaminodiphenylmethane, bis(4-aminophenyl)sulfide, 4,4'-diaminobenzanilide, dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3' -diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, oxydianiline, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide , 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 3,3′-diamino-4,4′-dichlorobenzophenone , 3,3′-diamino-4,4′-dimethoxybenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 2,2-bis(3-aminophenyl ) propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis( 4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfoxide, 4,4′-diamino-3,3 '-dimethyldiphenylmethane, 4,4'-diaminodiphenyl sulfoxide and the like.
３）ベンゼン核３つ以上のジアミン
１，３－ビス（３－アミノフェニル）ベンゼン、１，３－ビス（４－アミノフェニル）ベンゼン、１，４－ビス（３－アミノフェニル）ベンゼン、１，４－ビス（４－アミノフェニル）ベンゼン、１，３－ビス（４－アミノフェノキシ）ベンゼン、１，４－ビス（３－アミノフェノキシ）ベンゼン、１，４－ビス（４－アミノフェノキシ）ベンゼン、１，３－ビス（３－アミノフェノキシ）－４－トリフルオロメチルベンゼン、３，３’－ジアミノ－４－（４－フェニル）フェノキシベンゾフェノン、３，３’－ジアミノ－４，４’－ジ（４－フェニルフェノキシ）ベンゾフェノン、など。 3) diamines having three or more benzene nuclei 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1, 4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3′-diamino-4-(4-phenyl)phenoxybenzophenone, 3,3′-diamino-4,4′-di( 4-phenylphenoxy)benzophenone, and the like.
　そのほかに、３，３’－ビス（３－アミノフェノキシ）ビフェニル、３，３’－ビス（４－アミノフェノキシ）ビフェニル、４，４’－ビス（３－アミノフェノキシ）ビフェニル、４，４’－ビス（４－アミノフェノキシ）ビフェニル、ビス〔３－（３－アミノフェノキシ）フェニル〕エーテル、ビス〔３－（４－アミノフェノキシ）フェニル〕エーテル、ビス〔４－（３－アミノフェノキシ）フェニル〕エーテル、ビス〔４－（４－アミノフェノキシ）フェニル〕エーテルなどが挙げられる。 In addition, 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'- bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether , bis[4-(4-aminophenoxy)phenyl]ether and the like.
＜有機溶剤＞
　テトラカルボン酸二無水物とジアミンとの反応は、一般に有機溶剤中で行われる。テトラカルボン酸二無水物とジアミンとの反応に使用される有機溶剤は、テトラカルボン酸二無水物およびジアミンを溶解させることができ、テトラカルボン酸二無水物およびジアミンと反応しないものであれば特に限定されない。有機溶剤は単独でもちいてもよいし２種以上を混合して用いてもよく、適宜選択するとよい。
　例えば、テトラカルボン酸二無水物とジアミンとの反応に用いる有機溶剤の例としては、Ｎ－メチル－２－ピロリドン、Ｎ，Ｎ－ジメチルアセトアミド、Ｎ，Ｎ－ジエチルアセトアミド、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジエチルホルムアミド、Ｎ－メチルカプロラクタム、Ｎ，Ｎ，Ｎ’，Ｎ’－テトラメチルウレア等の含窒素極性溶剤；β－プロピオラクトン、γ－ブチロラクトン、γ－バレロラクトン、δ－バレロラクトン、γ－カプロラクトン、ジエチレングリコールジエチルエーテル、ジオキサン、テトラヒドロフラン、シクロペンタノン、シクロヘキサノン等の環状ケトン類、トルエン、キシレン等の芳香族類、シクロペンタン、シクロヘキサン等の脂環式化合物挙げられる。有機溶剤の使用量に特に制限はないが、生成するポリアミック酸の含有量が５～５０質量％とするのが望ましい。 <Organic solvent>
The reaction of tetracarboxylic dianhydride and diamine is generally carried out in an organic solvent. The organic solvent used for the reaction of the tetracarboxylic dianhydride and the diamine is particularly capable of dissolving the tetracarboxylic dianhydride and the diamine and not reacting with the tetracarboxylic dianhydride and the diamine. Not limited. The organic solvent may be used alone or in combination of two or more, and may be selected as appropriate.
For example, examples of organic solvents used in the reaction between tetracarboxylic dianhydride and diamine include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, and N,N-dimethylformamide. , N,N-diethylformamide, N-methylcaprolactam, N,N,N',N'-tetramethylurea and other nitrogen-containing polar solvents; β-propiolactone, γ-butyrolactone, γ-valerolactone, δ- Cyclic ketones such as valerolactone, γ-caprolactone, diethylene glycol diethyl ether, dioxane, tetrahydrofuran, cyclopentanone and cyclohexanone; aromatics such as toluene and xylene; and alicyclic compounds such as cyclopentane and cyclohexane. Although the amount of the organic solvent used is not particularly limited, it is desirable that the content of the polyamic acid to be produced is 5 to 50% by mass.
　ポリイミド前駆体溶液に用いる有機溶剤としては、使用するポリアミック酸またはポリイミド系樹脂を溶解しつつ微粒子を溶解しないものであればよい。
　ポリイミド前駆体溶液中の全成分のうち、有機溶剤の含有量は、５０～９５質量％が好ましく、６０～８５質量％がより好ましい。ポリイミド前駆体溶液における固形分は、５～５０質量％が好ましく、より１５～４０質量％がより好ましい
　ポリイミド前駆体溶液には、上記の成分のほかに、帯電防止、難燃性付与、低温焼成化、離型性、塗布性、低吸湿性、低線膨張率性、低下熱収縮性等を目的とし、帯電防止剤、難燃剤、化学イミド化剤、縮合剤、離型剤、表面調整剤、寸法安定剤など、適宜混合するとよい。 Any organic solvent may be used for the polyimide precursor solution as long as it dissolves the polyamic acid or polyimide resin used but does not dissolve the fine particles.
The content of the organic solvent in the polyimide precursor solution is preferably 50 to 95% by mass, more preferably 60 to 85% by mass. The solid content in the polyimide precursor solution is preferably 5 to 50% by mass, more preferably 15 to 40% by mass. Antistatic agents, flame retardants, chemical imidizing agents, condensing agents, release agents, surface control agents , a dimensional stabilizer, etc., may be mixed as appropriate.
　一例を示すと、ポリイミド多孔質フィルムのより具体的な製造手順は下記（１）～（６）のとおりであるが、シリカなど開孔用の無機粒子を用いて原反を多孔化する場合は無機粒子を除去するために原反を溶媒に浸漬する必要があるため、多孔化工程と焼成工程とを同時に実行することは難しい。この場合、焼成工程の前に多孔化工程を実施するのが望ましい。
　他方、樹脂製の粒子を用いて原反を多孔化する場合では、多孔化工程と焼成工程とを同時に実行することが可能となり製造工程をより簡便化ないしコンパクト化することが可能となる。
　ポリイミド多孔質フィルムの製造手順は次のとおり：
（１）カルボン酸無水物および有機アミン化合物から合成されるポリアミック酸を有するポリイミド前駆体溶液を調製する工程；
（２）ポリイミド前駆体溶液と微粒子とを混合したスラリーを作製する工程；
（３）スラリーを支持体上に塗工して無孔の原反を形成する原反形成工程； 
（４）原反形成工程で形成された原反を支持体から引き剥す剥離工程；
（５）剥離工程によって支持体から剥離された原反を多孔化する多孔化工程；および
（６）原反を焼成する焼成工程。 As an example, more specific manufacturing procedures for the polyimide porous film are as follows (1) to (6) below. Since it is necessary to immerse the original sheet in a solvent to remove the inorganic particles, it is difficult to perform the porosification process and the baking process at the same time. In this case, it is desirable to perform the porosification step before the firing step.
On the other hand, when resin particles are used to make the original fabric porous, the porous making process and the baking process can be performed simultaneously, and the manufacturing process can be simplified or made more compact.
The manufacturing procedure of polyimide porous film is as follows:
(1) preparing a polyimide precursor solution having a polyamic acid synthesized from a carboxylic anhydride and an organic amine compound;
(2) a step of preparing a slurry by mixing a polyimide precursor solution and fine particles;
(3) a raw fabric forming step of coating the slurry on a support to form a non-porous raw fabric;
(4) A peeling step of peeling off the original film formed in the original film forming step from the support;
(5) a porosification step of making the original sheet peeled from the support by the peeling step porous; and (6) a baking step of baking the original sheet.
［ポリイミド前駆体溶液の作製］
　上述したように、ポリアミック酸は、カルボン酸二無水物と有機アミン化合物とを重合することで得ることができる。ポリアミック酸に熱を付与することによってイミド化（熱イミド化）するか、もしくはポリアミック酸を化学的にイミド化（化学イミド化）することで、カルボン酸部分が閉環してポリイミド化することができる。
　イミド化率は約８０％以上、好ましくは８５％以上、より好ましくは９０％以上、さらに好ましくは９５％以上であることが望ましいが、ここも目的とする物性に合わせて調節するとよい。 [Preparation of polyimide precursor solution]
As described above, polyamic acid can be obtained by polymerizing a carboxylic acid dianhydride and an organic amine compound. By applying heat to the polyamic acid to imidize it (thermal imidization), or by chemically imidizing the polyamic acid (chemical imidization), the carboxylic acid moiety can be ring-closed to form a polyimide. .
The imidization rate is desirably about 80% or more, preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more, but this may also be adjusted according to the desired physical properties.
　カルボン酸無水物およびジアミンは上述したものを用いることができるが、今般の発明のポリイミド多孔質フィルムで使用されるポリアミック酸を調製するには、ジアミンは、フェニレンジアミン、ジメチルベンジジン、ジアミノジフェニルメタン、ジアミノジメチルジフェニルメタン、ｏ－ジアニシジン、９，９－ビス(４－アミノフェニル)フルオレンの中から選択される少なくとも１種であることが望ましく、中でもジメチルベンジジンが好ましい。
　また、カルボン酸は、ピロメリット酸二無水物、ビフェニルテトラカルボン酸、オキシジフタル酸無水物、ベンゾフェノンテトラカルボン酸二無水物、９，９－ビス（３，４－ジカルボキシフェニル）フルオレン二無水物から選択される少なくとも１種を含むことが望ましいが、リチウムイオン電池やリチウム金属電池において初期のクーロン効率を高めたいときは、Liを吸着ないし反応する性質がより低くできるポリイミドが望ましい。ベンゾフェノンテトラカルボン酸二無水物としては、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物が好ましい。すなわちカルボン酸としては、ピロメリット酸二無水物、４，４’－オキシジフタル酸無水物、３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物、９，９－ビス（３，４－ジカルボキシフェニル）フルオレン二無水物から選択される少なくとも１種であることが望ましい。 Carboxylic anhydrides and diamines mentioned above can be used, but for preparing the polyamic acid used in the polyimide porous film of the present invention, the diamines are phenylenediamine, dimethylbenzidine, diaminodiphenylmethane, diamino It is preferably at least one selected from dimethyldiphenylmethane, o-dianisidine and 9,9-bis(4-aminophenyl)fluorene, with dimethylbenzidine being particularly preferred.
In addition, the carboxylic acid can be selected from pyromellitic dianhydride, biphenyltetracarboxylic acid, oxydiphthalic anhydride, benzophenonetetracarboxylic dianhydride, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride. Although it is desirable to contain at least one selected type, when it is desired to increase the initial coulombic efficiency in a lithium ion battery or a lithium metal battery, a polyimide capable of lowering the property of adsorbing or reacting to Li is desirable. As the benzophenonetetracarboxylic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride is preferred. That is, the carboxylic acids include pyromellitic dianhydride, 4,4′-oxydiphthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 9,9-bis(3,4 -Dicarboxyphenyl)fluorene dianhydride is preferably at least one selected from.
　ジアミンに関して、フェニレンジアミンとしてｏ－フェニレンジアミン、ｍ－フェニレンジアミン、ｐ－フェニレンジアミンのうちｍ－フェニレンジアミンおよびｐ－フェニレンジアミンが好ましく、ｐ－フェニレンジアミンがさらに好ましい。また、ジメチルベンジジンとしては２，２’－ジメチルベンジジンおよび３，３’－ジメチルベンジジンのうち、２，２’－ジメチルベンジジンが好ましい。
　ジアミノジフェニルメタンとしては、３，３’－ジアミノジフェニルメタン、３，４’－ジアミノジフェニルメタン、４，４’－ジアミノジフェニルメタンがあるが、なかでも４，４’－ジアミノジフェニルメタンが好ましい。ジアミノジメチルジフェニルメタンとしては、４，４’－ジアミノ－３, ３’－ジメチルジフェニルメタンが好ましい。
　総ずると、ジアミンは、ｐ－フェニレンジアミン、２，２’－ジメチルベンジジン、４，４’－ジアミノジフェニルメタン、４，４’－ジアミノ－３,３’－ジメチルジフェニルメタン、ｏ－ジアニシジン、９，９－ビス(４－アミノフェニル)フルオレンの中から選択される少なくとも１種であることが望ましい。ジアミンは１種でもよいし、２種以上を混合してもよい。 Regarding diamines, among o-phenylenediamine, m-phenylenediamine and p-phenylenediamine, m-phenylenediamine and p-phenylenediamine are preferable as phenylenediamine, and p-phenylenediamine is more preferable. As dimethylbenzidine, 2,2'-dimethylbenzidine is preferred among 2,2'-dimethylbenzidine and 3,3'-dimethylbenzidine.
Diaminodiphenylmethane includes 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenylmethane is preferred. Diaminodimethyldiphenylmethane is preferably 4,4'-diamino-3,3'-dimethyldiphenylmethane.
Collectively, the diamines are p-phenylenediamine, 2,2′-dimethylbenzidine, 4,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′-dimethyldiphenylmethane, o-dianisidine, 9,9 At least one selected from -bis(4-aminophenyl)fluorene is desirable. One type of diamine may be used, or two or more types may be mixed.
　上述したように、ポリアミック酸を重合するための溶媒としては例えば有機極性溶媒を用いることができ、好ましい有機極性溶媒としては、例えば、テトラメチル尿素、フェノール、Ｎ－メチル－２－ピロリドン（ＮＭＰ）、ピリジン、Ｎ，Ｎ－ジメチルアセトアミド（ＤＭＡｃ）、Ｎ，Ｎ－ジメチルホルムアミド、ｐ－クロロフェノール、ｏ－クロルフェノール、ジメチルスルホキシド、クレゾールが挙げられる。 As described above, for example, an organic polar solvent can be used as the solvent for polymerizing the polyamic acid. Preferred organic polar solvents include, for example, tetramethylurea, phenol, N-methyl-2-pyrrolidone (NMP) , pyridine, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, p-chlorophenol, o-chlorophenol, dimethylsulfoxide, and cresol.
　ポリアミック酸を作製するときの他の条件としては、例えば、テトラカルボン酸二無水物およびジアミンをだいたい等モル（略等モル）で、好ましくは約８０℃以下、より好ましくは７０℃以下、さらに好ましくは０～６５℃、特に好ましくは１０～６０℃の温度条件下で反応させるとよい。
　反応時間としては、好ましくは約０．１時間以上、より好ましくは０．２～７２時間、さらに好ましくは０．５～６０時間で反応させることで、ポリアミック酸を作製することができる。なお、ポリイミド前駆体溶液を製造するときに、分子量を調整するための成分を反応溶液に加えることもできる。
　作製されたポリイミド前駆体溶液は、例えばポリアミック酸５～５０質量％と有機極性溶媒５０～９５質量％とからなる。ポリアミック酸の含有量が５質量％未満だと多孔質ポリイミド膜を作製した際のフィルム強度が低下し、５０質量％を超えると多孔質ポリイミド膜の粘度が高くなりすぎ、ハンドリング性が低下する。 Other conditions for producing the polyamic acid include, for example, approximately equimolar (substantially equimolar) amounts of tetracarboxylic dianhydride and diamine, preferably about 80° C. or lower, more preferably 70° C. or lower, and still more preferably should be reacted at a temperature of 0 to 65°C, preferably 10 to 60°C.
The reaction time is preferably about 0.1 hour or more, more preferably 0.2 to 72 hours, and still more preferably 0.5 to 60 hours, whereby a polyamic acid can be produced. A component for adjusting the molecular weight can also be added to the reaction solution when producing the polyimide precursor solution.
The prepared polyimide precursor solution comprises, for example, 5 to 50% by mass of polyamic acid and 50 to 95% by mass of organic polar solvent. If the content of the polyamic acid is less than 5% by mass, the film strength of the porous polyimide film produced is reduced, and if it exceeds 50% by mass, the viscosity of the porous polyimide film becomes too high, resulting in poor handleability.
［スラリー作製］
　上述したポリイミド前駆体溶液と微粒子とを混合してスラリーを作製する。スラリーには濃度調整用の有機溶剤、さらには帯電防止、低温焼成化、離型性、塗布性、低吸湿性、低線膨張率性、化学イミド化剤など既に述べた添加材を加えてもよい。
　スラリーはポリイミド前駆体溶液５～９０質量%と開孔用の微粒子２～４０%、濃度調整用に有機溶剤を０～９５質量%、添加剤については特に限定されないが好ましくは０～２０質量%からなり、それらを攪拌装置で混合する。なお攪拌では「あわとり練太郎」（（株）シンキー製）などの自転公転攪拌機を用いるとよい。 [Slurry preparation]
A slurry is prepared by mixing the polyimide precursor solution and the fine particles described above. Additives such as an organic solvent for concentration adjustment, antistatic, low-temperature baking, releasability, coatability, low hygroscopicity, low coefficient of linear expansion, and chemical imidizing agents can be added to the slurry. good.
The slurry contains 5 to 90% by mass of the polyimide precursor solution, 2 to 40% by mass of fine particles for opening, 0 to 95% by mass of an organic solvent for adjusting the concentration, and the additive is not particularly limited, but preferably 0 to 20% by mass. which are mixed with an agitator. For stirring, it is recommended to use a rotation-revolution stirrer such as "Awatori Mixer" (manufactured by Thinky Co., Ltd.).
　スラリーの溶液粘度は、塗工で使用するダイやコータマシンの特性に応じて適宜決めるとよい。例えば、塗工のしやすさやフィルム強度の観点から、例えば０．１～１０００Ｐａ・ｓ、好ましくは０．５～３００Ｐａ・ｓ、更に好ましくは１～２５０Ｐａ・ｓ程度の粘度とすることで様々なダイやコータマシンで使用することができる。 The solution viscosity of the slurry should be determined appropriately according to the characteristics of the die and coater machine used for coating. For example, from the viewpoint of ease of coating and film strength, various Can be used in dies and coater machines.
［原反形成工程］
　作製したスラリーを支持体上に塗工して原反を形成することができる。塗工方法については特に制限はなく、例えば、スラリーブレードやＴダイなどを用いてガラス板、ステンレス板、ＰＥＴ（ポリエチレンテレフタレート）フィルム、ＰＥＮ（ポリエチレンナフタレート）フィルム等の支持体の上に塗工する。これにより、支持体上にスラリーが層状に拡がった原反を形成することができる。
　また、支持体としては金属ベルトなどの無端機構のほか、樹脂フィルムを用いるとよい。支持体としては、作製したスラリーの影響を受けない、あるいは影響を受けにくいものであればよく、無端機構であればステンレスなどの金属製、樹脂フィルムであればＰＥＴやポリテトラフルオロエチレンなどの樹脂を用いるとよい。 [Original fabric forming process]
The produced slurry can be coated on a support to form a raw fabric. The coating method is not particularly limited. For example, a slurry blade, a T-die, or the like is used to coat a support such as a glass plate, a stainless steel plate, a PET (polyethylene terephthalate) film, a PEN (polyethylene naphthalate) film, or the like. do. As a result, it is possible to form a raw fabric in which the slurry spreads in layers on the support.
As the support, a resin film may be used in addition to an endless mechanism such as a metal belt. Any support may be used as long as it is unaffected or hardly affected by the prepared slurry. The endless mechanism is made of metal such as stainless steel, and the resin film is made of resin such as PET or polytetrafluoroethylene. should be used.
［剥離工程］
　支持体上に原反を形成した後であって焼成工程の前の適切なタイミングで支持体から原反を剥離する。原反の長さとしては特に制限はないが、生産性の観点から長尺（例えば、５ｍ以上）であることが好ましく、１０ｍ以上であることがより好ましく、２０ｍ以上であることが更に好ましい。原反の長さの上限値としては特に制限はないが、例えば、４０００ｍ以下であり、典型的には１０００ｍ以下にすると原反の取り扱いが容易になる。原反を支持体からより容易に剥離するために原反を適切に乾燥させるとよい。 [Peeling process]
After the original fabric is formed on the support, the original fabric is peeled off from the support at an appropriate timing before the baking step. The length of the original fabric is not particularly limited, but from the viewpoint of productivity, it is preferably long (for example, 5 m or longer), more preferably 10 m or longer, and even more preferably 20 m or longer. Although the upper limit of the length of the original fabric is not particularly limited, it is, for example, 4000 m or less, and typically 1000 m or less facilitates handling of the original fabric. It is preferable to properly dry the original sheet in order to separate the original sheet from the support more easily.
［多孔化工程］
　支持体から剥離した原反から微粒子を適切な方法を選択して除去することにより、球状または略球状の孔を有するポリイミド多孔質フィルムを製造することができる。微粒子の除去方法としては溶媒や酸、アルカリで微粒子を溶かして除去する方法や、焼成によって微粒子を除去する方法があるが、これは用いる微粒子に依存する。生産性やコストを鑑みると、開孔を形成するための微粒子としては樹脂粒子が好ましい。
　開孔粒子として、シリカ等の無機粒子を用いる場合、酸やアルカリと接触させて無機粒子を溶解させることにより除去することができる。
　微粒子が樹脂粒子である場合、ポリイミドフィルムを溶解せず、樹脂粒子が可溶な有機溶剤により、樹脂粒子を溶解除去することができる。このような有機溶剤としては、例えば、テトラヒドロフラン等のエーテル類；トルエン等の芳香族類；アセトンなどのケトン類；酢酸エチルなどのエステル類；が挙げられる。これらの中でも、テトラヒドロフラン等のエーテル類が好ましく、テトラヒドロフランを用いることがさらに好ましい。また樹脂微粒子の場合は、樹脂微粒子の熱分解温度以上、かつ、ポリイミド系樹脂の熱分解温度未満の温度に加熱することで樹脂微粒子を分解させて除去することで開孔を形成することができる。 [Porosification step]
A polyimide porous film having spherical or approximately spherical pores can be produced by selecting an appropriate method to remove the fine particles from the raw film peeled from the support. As methods for removing fine particles, there are a method of removing fine particles by dissolving them with a solvent, an acid or an alkali, and a method of removing fine particles by firing, but this depends on the fine particles used. In view of productivity and cost, resin particles are preferable as fine particles for forming pores.
When inorganic particles such as silica are used as the open-pore particles, they can be removed by bringing them into contact with acid or alkali to dissolve the inorganic particles.
When the fine particles are resin particles, the resin particles can be dissolved and removed with an organic solvent in which the resin particles are soluble but the polyimide film is not dissolved. Examples of such organic solvents include ethers such as tetrahydrofuran; aromatics such as toluene; ketones such as acetone; and esters such as ethyl acetate. Among these, ethers such as tetrahydrofuran are preferred, and tetrahydrofuran is more preferred. In the case of fine resin particles, openings can be formed by heating to a temperature equal to or higher than the thermal decomposition temperature of the fine resin particles and lower than the thermal decomposition temperature of the polyimide resin to decompose and remove the fine resin particles. .
［焼成工程］
　得られた原反もしくは多孔化された原反に熱を付与してイミド化（以降、熱イミド化という）し、これによりポリイミド多孔質フィルムを形成することができる。この熱イミド化後のポリイミド多孔質フィルムの機械方向（ＭＤ方向）の収縮率は５％以下、また幅方向（ＴＤ方向）の収縮率も５％以下に抑制するとよい。収縮率の抑制手段や方法に特に制限はないが、原反や開孔後のフィルムにかかるテンションを低減するとよい。
　温度条件は、例えば２５０～５００℃の温度範囲で、１～３００分、好ましくは５～２４０分間、より好ましくは１０～１２０分間で適宜実行するとよい。生産性を高めるには加熱焼成時間はなるべく短くすることが望ましい。
　この熱イミド化処理では、２００℃以上の温度域での昇温速度が、２０℃／分以上、好ましくは３０℃／分以上であることが望ましい。イミド化反応が顕著に起こる１００～２５０℃の温度域において上記の昇温速度で加熱することにより、表面開口率および孔径が大幅に向上した本発明の多孔質ポリイミド膜を得ることができる。
　焼成温度はポリアミック酸の種類や目的とするイミド化の度合いによっても異なるが、１２０～５００℃が好ましく、１５０～５００℃がさらに好ましい。
　焼成を行う際は、乾燥工程と焼成工程とを分けてもよいが、厳密に分けずに実施してもよい。例えば、３６０℃で焼成を行う場合、室温から３６０℃まで連続的に昇温させた後に３６０℃で数十分間焼成する方法や、室温から３６０℃まで段階的に昇温させて３６０℃で数十分間焼成する方法があるが、適宜好ましい手順を選択するとよい。室温から昇温させていく途中の適切なタイミングで支持体から原反を剥離すればよい。 [Baking process]
Heat is applied to the obtained raw film or porous raw film to imidize it (hereinafter referred to as thermal imidization), whereby a polyimide porous film can be formed. The shrinkage rate in the machine direction (MD direction) of the polyimide porous film after thermal imidization should be suppressed to 5% or less, and the shrinkage rate in the width direction (TD direction) should also be suppressed to 5% or less. There is no particular limitation on the means or method for suppressing the shrinkage rate, but it is preferable to reduce the tension applied to the original fabric or the film after perforation.
The temperature conditions are, for example, a temperature range of 250 to 500° C. and a time of 1 to 300 minutes, preferably 5 to 240 minutes, more preferably 10 to 120 minutes. In order to improve productivity, it is desirable to shorten the heating and baking time as much as possible.
In this thermal imidization treatment, it is desirable that the heating rate in the temperature range of 200° C. or higher is 20° C./min or more, preferably 30° C./min or more. The porous polyimide film of the present invention having significantly improved surface open area ratio and pore size can be obtained by heating at the above-described temperature increase rate in the temperature range of 100 to 250° C. where the imidization reaction occurs remarkably.
The firing temperature varies depending on the type of polyamic acid and the intended degree of imidization, but is preferably 120 to 500.degree. C., more preferably 150 to 500.degree.
When firing, the drying step and the firing step may be separated, but they may be carried out without strict separation. For example, when firing at 360 ° C., a method of continuously raising the temperature from room temperature to 360 ° C. and then firing at 360 ° C. for several tens of minutes, or a method of stepwise raising the temperature from room temperature to 360 ° C. and firing at 360 ° C. Although there is a method of firing for several tens of minutes, it is preferable to select a suitable procedure. The raw fabric may be peeled off from the support at an appropriate timing while the temperature is being raised from room temperature.
　焼成されたポリイミド多孔質フィルムは、例えば直径２．５ｃｍ（１インチ）以上２５ｃｍ（１０インチ）以下の巻き芯に捲回するとよい。巻き芯の直径としては５ｃｍ（２インチ）以上１０ｃｍ（４インチ）以下が好ましい。巻き芯の材質としては特に制限はないが、紙、ステンレスなどの金属製、ＡＢＳやＰＰ、ＰＥ、ＰＶＣ、ＰＥＴ、ＦＲＰ、ベークライトなどの硬質プラスチック製が挙げられる。 The baked polyimide porous film is preferably wound around a winding core having a diameter of 2.5 cm (1 inch) or more and 25 cm (10 inches) or less. The diameter of the winding core is preferably 5 cm (2 inches) or more and 10 cm (4 inches) or less. The material of the winding core is not particularly limited, but includes paper, metal such as stainless steel, and hard plastic such as ABS, PP, PE, PVC, PET, FRP, and bakelite.
　上記の焼成工程が樹脂粒子の除去を兼ねるとき、樹脂粒子を構成する有機材料が、ポリイミドよりも低温で分解するものであれば、ポリイミドに熱的なダメージを与えることなく樹脂粒子のみを消失させることができる。このため樹脂微粒子の分解温度は例えば、１２０℃以上５００℃以下であることが好ましい。 When the above baking step also serves as the removal of the resin particles, if the organic material constituting the resin particles decomposes at a lower temperature than the polyimide, only the resin particles disappear without causing thermal damage to the polyimide. be able to. Therefore, the decomposition temperature of the fine resin particles is preferably, for example, 120° C. or higher and 500° C. or lower.
［アルカリエッチング］
　ポリイミド多孔質フィルムの製造において、微粒子を除去する前の原反の少なくとも一部を除去するか、または微粒子を除去した後のポリイミド多孔質フィルムの少なくとも一部を除去するために、アルカリエッチングを行ってもよい。 [Alkaline etching]
In the production of the polyimide porous film, alkali etching is performed in order to remove at least part of the original film before removing the fine particles, or to remove at least part of the polyimide porous film after removing the fine particles. may
　上記の手順で作製されたポリイミド多孔質フィルムは、複数の球状孔または略球状孔が内部に形成されており、孔の少なくとも一部が互いに連通している。ポリイミド多孔質フィルム表面や内部の孔径は、フィルムを製造する際に使用する微粒子の種類やサイズを適宜選択ないし調整することによりコントロールすることができる。
　本発明のポリイミド多孔質フィルムにおいて、孔は孔径のばらつきが少なく、また、分布もより均一であることが好ましい。フィルム内の孔の孔径や分布のばらつきの少なさを示す指標として、フィルムのガーレ値を場所を変えて数点測定し、その際の値のばらつきを評価する方法を用いることができる。ポリイミド多孔質フィルムの任意の１０点について、ＪＩＳ Ｐ ８１１７に準拠し、ガーレ法により透気度（１００ｍＬの空気がフィルムを透過する秒数）を測定し、透気度の平均値と標準偏差とを求めることができる。 The polyimide porous film produced by the above procedure has a plurality of spherical or substantially spherical pores formed therein, and at least some of the pores communicate with each other. The pore size on the surface and inside of the polyimide porous film can be controlled by appropriately selecting or adjusting the type and size of fine particles used when producing the film.
In the polyimide porous film of the present invention, it is preferable that the pore diameters are less varied and have a more uniform distribution. As an index indicating the degree of variation in the pore size and distribution of pores in the film, a method of measuring the Gurley value of the film at several points at different locations and evaluating the variation in the values at that time can be used. For arbitrary 10 points of the polyimide porous film, according to JIS P 8117, the air permeability (number of seconds for 100 mL of air to pass through the film) is measured by the Gurley method, and the average value and standard deviation of the air permeability can be asked for.
　孔径や分布のばらつきの小さい孔を有するフィルムは、フィルムの製造時に、真球率が高く、粒径分布指数の小さい微粒子を用いることや、微粒子とポリアミック酸またはポリイミド系樹脂とを含むポリイミド前駆体溶液の粘度を均一な塗布が可能となるような適切な粘度に調整すること等により製造することができる。
　上記の方法で測定したガーレ法による透気度は４００秒以下が好ましく、３００秒以下であることがより好ましく、２５０秒以下がより好ましい。このような透気度となることにより、リチウムやリチウムイオンをより低抵抗に移動させることができるものと考えられる。 A film having pores with small variations in pore size and distribution can be produced by using fine particles with a high sphericity and a small particle size distribution index, or by using a polyimide precursor containing fine particles and a polyamic acid or polyimide resin. It can be manufactured by adjusting the viscosity of the solution to an appropriate viscosity that enables uniform coating.
The air permeability measured by the Gurley method as described above is preferably 400 seconds or less, more preferably 300 seconds or less, and even more preferably 250 seconds or less. It is considered that such an air permeability allows lithium and lithium ions to move with lower resistance.
　本発明のポリイミド多孔質フィルムの膜厚は、フィルムを電池用セパレータとして使用する場合には、２μｍ以上１００μｍ以下が好ましく、３μｍ以上８０μｍ以下がより好ましく、４μｍ以上５０μｍ以下がさらに好ましい。膜厚はマイクロメータ等で複数の箇所の厚さを測定し平均することで求めることができる。 When the film is used as a battery separator, the film thickness of the polyimide porous film of the present invention is preferably 2 μm or more and 100 μm or less, more preferably 3 μm or more and 80 μm or less, and even more preferably 4 μm or more and 50 μm or less. The film thickness can be obtained by measuring the thickness at a plurality of locations with a micrometer or the like and averaging the thickness.
　［ポリイミド多孔質フィルムの用途］
　本発明のポリイミド多孔質フィルムは、ニッケルカドミウム電池、ニッケル水素電池、負極に黒鉛を用いるリチウムイオン一次／二次電池、負極に金属リチウムを用いるリチウム金属一次／二次電池などの蓄電デバイスにおいてセパレータとして使用することができる。これらの中でもリチウムイオン二次電池用もしくはリチウム金属二次電池用のセパレータとして用いることが好ましい。また本発明のポリイミド多孔質フィルムは燃料電池用の電解質膜や電子回路用の基板として用いてもよい。 [Applications of polyimide porous film]
The polyimide porous film of the present invention can be used as a separator in electricity storage devices such as nickel-cadmium batteries, nickel-hydrogen batteries, lithium-ion primary/secondary batteries using graphite for the negative electrode, and lithium-metal primary/secondary batteries using metallic lithium for the negative electrode. can be used. Among these, it is preferable to use it as a separator for a lithium ion secondary battery or a lithium metal secondary battery. The polyimide porous film of the present invention may also be used as an electrolyte membrane for fuel cells or as a substrate for electronic circuits.
　本発明のポリイミド多孔質フィルムをセパレータとして用いる蓄電デバイスは、セパレータのほか、負極、正極、および電解液を含む。蓄電デバイスの形式としては捲回型（外観は円筒や角型）、ラミネート型、コイン型など様々な形式があり、正極、セパレータ、および負極が順に積層された電極構造体が外装体に内容され、この外装体内に電解液が注液され蓄電デバイスが作製される。 A power storage device using the polyimide porous film of the present invention as a separator includes a separator, a negative electrode, a positive electrode, and an electrolytic solution. Electricity storage devices come in a variety of formats, including a wound type (cylindrical or rectangular in appearance), a laminate type, and a coin type. , and the electrolyte is injected into the exterior body to fabricate an electricity storage device.
　リチウムイオン電池の負極は、例えば負極活物質、導電助剤およびバインダからなる負極合剤が、集電体上に成形された構造をとる。負極活物質として、リチウムを電気化学的にドープすることが可能な材料が採用でき、このような活物質としては例えば、炭素材料、シリコン、アルミニウム、スズ、ウッド合金等が挙げられる。なおリチウム金属電池の場合は周知のように負極として金属リチウムを用いる。 The negative electrode of a lithium-ion battery has a structure in which, for example, a negative electrode mixture consisting of a negative electrode active material, a conductive aid, and a binder is formed on a current collector. A material that can be electrochemically doped with lithium can be used as the negative electrode active material, and examples of such an active material include carbon materials, silicon, aluminum, tin, and Wood's alloys. In the case of lithium metal batteries, metallic lithium is used as the negative electrode, as is well known.
　負極を構成する導電助剤としては、アセチレンブラック、ケッチェンブラックといった炭素材料が挙げられる。バインダは有機高分子からなり、例えば、ポリフッ化ビニリデン、カルボキシメチルセルロース等が挙げられる。集電体には、銅箔、ステンレス箔、ニッケル箔等を用いることが可能である。 Carbon materials such as acetylene black and ketjen black are examples of the conductive aids that make up the negative electrode. The binder is made of an organic polymer, and examples thereof include polyvinylidene fluoride, carboxymethyl cellulose, and the like. A copper foil, a stainless foil, a nickel foil, or the like can be used as the current collector.
　また、正極は、正極活物質、導電助剤およびバインダからなる正極合剤が、集電体上に成形された構造とすることができる。例えば、正極活物質としては、ニッケルカドミウム電池の場合は水酸化ニッケルを、ニッケル水素電池の場合は水酸化ニッケルやオキシ水酸化ニッケルを、それぞれ用いることができる。リチウムイオン二次電池の場合、正極活物質としては、リチウム含有遷移金属酸化物等が挙げられ、具体的にはＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎ０．５Ｎｉ０．５Ｏ２、ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＭｎ２Ｏ４、ＬｉＦｅＰＯ４、ＬｉＣｏ０．５Ｎｉ０．５Ｏ２、ＬｉＡｌ０．２５Ｎｉ０．７５Ｏ２等が挙げられる。導電助剤はアセチレンブラック、ケッチェンブラックといった炭素材料が挙げられる。 In addition, the positive electrode can have a structure in which a positive electrode mixture comprising a positive electrode active material, a conductive aid, and a binder is formed on a current collector. For example, as the positive electrode active material, nickel hydroxide can be used in the case of nickel-cadmium batteries, and nickel hydroxide or nickel oxyhydroxide can be used in the case of nickel-hydrogen batteries. In the case of a lithium ion secondary battery, examples of the positive electrode active material include lithium-containing transition metal oxides. , LiCo0.5Ni0.5O2, LiAl0.25Ni0.75O2, and the like. Carbon materials such as acetylene black and ketjen black can be used as conductive aids.
　リチウムイオン電池やリチウム金属電池の電解液は、リチウム塩を非水系溶媒に溶解した非水電解液が典型的に使用されるが、求める特性に応じて水系電解液を使用してもよい。リチウム塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＦＳＩ等が挙げられる。非水系溶媒としては、プロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、γ－ブチロラクトン、ビニレンカーボネート等が挙げられ、これらは単独で用いてもよいし添加剤を混合して用いてもよい。 A non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent is typically used as the electrolyte for a lithium ion battery or a lithium metal battery, but an aqueous electrolyte may be used depending on desired characteristics. Lithium salts include LiPF 6 , LiBF 4 , LiClO 4 , LiFSI and the like. Examples of non-aqueous solvents include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, vinylene carbonate, etc. These may be used alone or mixed with additives. good too.
　外装材は、金属缶またはアルミラミネートパック等が挙げられる。電池の形状は角型、円筒型、コイン型等があるが、本発明のセパレータはいずれの形状においても好適に適用することが可能である。
　一例として、以下にラミネート型電池、円筒電池、およびコイン電池の作製手順について説明する。
［ラミネート型リチウムイオン二次電池およびリチウム金属二次電池］
［正極・負極］
　正極および負極としてそれぞれ市販品を使用することができ、例えば、正極に含まれる正極活物質はスピネル構造を有するＬｉ１．１Ｍｎ１．９Ｏ４と、リチウム・ニッケル・コバルト・マンガン酸リチウム（Ｎｉ／Ｌｉモル比０．７）との混合物であり、バインダとしてポリフッ化ビニリデン、導電助剤としてカーボンブラック粉末を用いることができる。 Exterior materials include metal cans, aluminum laminate packs, and the like. Batteries may be rectangular, cylindrical, coin-shaped, or the like, and the separator of the present invention can be suitably applied to any shape.
As an example, the procedure for producing a laminate type battery, a cylindrical battery, and a coin battery will be described below.
[Laminated Lithium Ion Secondary Battery and Lithium Metal Secondary Battery]
[Positive electrode/negative electrode]
Commercially available products can be used as the positive electrode and the negative electrode. For example, the positive electrode active material contained in the positive electrode is Li 1.1 Mn 1.9 O 4 having a spinel structure, and lithium-nickel-cobalt-lithium manganate ( Ni/Li molar ratio of 0.7), polyvinylidene fluoride can be used as the binder, and carbon black powder can be used as the conductive aid.
　負極には負極活物質として黒鉛などを用いることができ、正極活物質層および負極活物質層の空孔率と空孔径は適宜調整するとよい。正極および負極の集電体の一方の面側の活物質層を剥がし、例えば２９ｍｍ×４０ｍｍのサイズに切り抜いて使用する。また黒鉛のかわりに金属リチウム層を所定の厚さで形成して負極として使用することもできる。この場合、エネルギー密度の向上が期待できる。 Graphite or the like can be used as a negative electrode active material for the negative electrode, and the porosity and pore diameter of the positive electrode active material layer and the negative electrode active material layer can be adjusted as appropriate. The active material layer on one side of the current collectors of the positive electrode and the negative electrode is peeled off, and cut into a size of 29 mm×40 mm, for example, for use. Also, instead of graphite, a metal lithium layer can be formed with a predetermined thickness and used as the negative electrode. In this case, an improvement in energy density can be expected.
　正極の正極集電体にアルミニウム製の正極タブを溶接し、負極の負極集電体に銅製の負極タブ（負極集電板）を溶接する。これらタブを溶接した正極の正極活物質層と負極の負極活物質層とを対向させ、間にセパレータを挟んでプレート状の１つの電極構造体を作製する。 An aluminum positive electrode tab is welded to the positive electrode current collector of the positive electrode, and a copper negative electrode tab (negative electrode current collector plate) is welded to the negative electrode current collector of the negative electrode. The positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode, to which these tabs are welded, are opposed to each other, and a separator is sandwiched therebetween to form one plate-shaped electrode structure.
　アルミ層が設けられたラミネートフィルムによる外装材（サイズおよび形状は例えば６０ｍｍ×６０ｍｍの方形状）を用いて上述の電極構造体を挟み込み、方形状の４辺のうちの３辺を熱で圧着封止して外装体を形成する。
　この外装体に、真空含浸装置（例えばＴＯＳＰＡＣＫ  Ｖ－３０７ＧＩＩ；東静電気株式会社製）を用いて電解液を注入して、残りの１辺を熱圧着で真空封止してセルを作製する。その後、注液した電解液が電極構造体の細孔に十分含浸するまで、例えば室温で所定時間静置するとよい。 The above-described electrode structure is sandwiched using an exterior material (size and shape is, for example, a square of 60 mm × 60 mm) made of a laminate film provided with an aluminum layer, and three of the four sides of the square are heat-sealed by pressure bonding. It stops and forms an exterior body.
An electrolytic solution is injected into this outer package using a vacuum impregnation device (eg, TOSPACK V-307GII; manufactured by Todeneki Co., Ltd.), and the remaining one side is vacuum-sealed by thermocompression bonding to prepare a cell. After that, it is preferable to leave the electrode structure at rest for a predetermined time, for example, until the pores of the electrode structure are sufficiently impregnated with the injected electrolytic solution.
［捲回型リチウムイオン二次電池／リチウム金属電池］
　捲回型のリチウムイオン二次電池／リチウム金属二次電池（以降、リチウム二次電池という）は、例えば、電極構造体が非水電解液と共に円筒形状の外装体に収容された構成を有する。捲回型のリチウム二次電池における電極構造体は、それぞれ帯状にした正極、負極、２枚のセパレータを準備し、これらを重ねて層状に巻くことで作製される。この電極構造体を円筒形状の外装体に収容し、この外装体内に電解液を注液して封をすることで捲回型の電池が作製される。 [Wound Lithium Ion Secondary Battery/Lithium Metal Battery]
A wound type lithium ion secondary battery/lithium metal secondary battery (hereinafter referred to as a lithium secondary battery) has, for example, a configuration in which an electrode structure is housed in a cylindrical exterior body together with a non-aqueous electrolyte. An electrode structure in a wound-type lithium secondary battery is produced by preparing a strip-shaped positive electrode, a negative electrode, and two separators, and stacking and winding them in layers. This electrode structure is accommodated in a cylindrical outer package, and an electrolytic solution is poured into the outer package and sealed to produce a wound type battery.
　捲回型のリチウム二次電池では、例えば、長尺シート状の正極集電体と、正極活物質を含み且つ正極集電体上に設けられた正極合材層とで構成される正極を用いる。また、長尺シート状の負極集電体と、負極活物質を含み且つ負極集電体上に設けられた負極合材層と、で構成された負極を用いることができる。
　セパレータは、正極および負極と同様に、長尺シート状に形成され、このセパレータを上述した正極および負極の間に介装した状態で捲回する。 A wound-type lithium secondary battery uses a positive electrode composed of, for example, a long sheet-like positive electrode current collector and a positive electrode mixture layer containing a positive electrode active material and provided on the positive electrode current collector. . Further, a negative electrode composed of a long sheet-like negative electrode current collector and a negative electrode mixture layer containing a negative electrode active material and provided on the negative electrode current collector can be used.
The separator is formed in a long sheet like the positive electrode and the negative electrode, and the separator is wound while being interposed between the positive electrode and the negative electrode.
　外装体は、有底円筒状のケース本体と、ケース本体の開口部を塞ぐ蓋とを備える。蓋およびケース本体は例えば金属製であり、互いに絶縁されている。蓋は正極集電体に電気的に接続され、ケース本体は負極集電体に電気的に接続されている。蓋が正極端子、ケース本体が負極端子をそれぞれ兼ねるようにしてもよい。 The exterior body includes a bottomed cylindrical case body and a lid that closes the opening of the case body. The lid and case body are made of metal, for example, and are insulated from each other. The lid is electrically connected to the positive electrode current collector, and the case body is electrically connected to the negative electrode current collector. The lid may also serve as the positive terminal, and the case body may also serve as the negative terminal.
　リチウム二次電池は、例えば－１０～８０℃で充放電することができる。電池内の内圧上昇の対策として、電池の蓋に安全弁を設ける対策や、電池のケース本体やこのケース本体に組み合わせられるガスケットに切り込みを入れる対策を採用することができる。また、過充電防止のために電池の内圧を感知して電流を遮断する電流遮断機構を蓋に設けることもできる。 Lithium secondary batteries can be charged and discharged at -10 to 80°C, for example. As countermeasures against an increase in the internal pressure inside the battery, it is possible to adopt measures such as providing a safety valve in the lid of the battery, or cutting a notch in the case body of the battery or in the gasket that is combined with this case body. In addition, the lid may be provided with a current interrupting mechanism that detects the internal pressure of the battery and interrupts the current to prevent overcharging.
　以下、実施例を示して本発明を更に具体的に説明するが、本発明の範囲は、これらの実施例に限定されるものではない。
［膜厚］
　接触式厚み計（ピーコック製）により測定した。 EXAMPLES The present invention will be described in more detail below with reference to Examples, but the scope of the present invention is not limited to these Examples.
[Thickness]
It was measured with a contact-type thickness gauge (manufactured by Peacock).
［ガーレ値（透気度）］
　製造した微多孔膜からＭＤ方向に８０ｍｍ、全幅の試験片を採取し、中央部と左右の端部（端面から５０ｍｍ内側）の３点について、Ｂ型ガーレ式デンソメーター（熊谷理機工業株式会社 型録No.２０６０）を用い、ＪＩＳ　Ｐ８１１７に準じて、測定を行った。３点の平均値をガーレ値として算出した。 [Gurley value (air permeability)]
A test piece with a width of 80 mm in the MD direction was taken from the manufactured microporous membrane, and three points at the center and left and right ends (50 mm inside from the end surface) were measured with a B-type Gurley densometer (Kumagaya Law of nature machine industry Co., Ltd.) Model No. 2060) was used, and measurement was performed according to JIS P8117. The average value of 3 points was calculated as the Gurley value.
［空孔率（重量法）］
　３．５×４．５ｃｍの大きさの多孔質フィルムを２０枚打ち抜き、合計の大きさが３１５ｃｍ２になるような面積の多孔質フィルムを用意し、膜厚と重量を測定した。
　測定に際し、真密度測定装置 (BELPycno : マイクロトラック・ベル社製)を用いて多孔質フィルムの真密度を測定した。測定セルの大きさは３．５ｃｃのものを使用し、得られた真密度の結果をＤ、多孔質フィルムの面積をＳ、膜厚をｄ、重量をｗとして次式により空孔率を算出した：
　空孔率＝（１－（ｗ／（Ｓ×ｄ×Ｄ）×１００ 　 （１）  [Porosity (weight method)]
Twenty porous films each having a size of 3.5×4.5 cm were punched out to prepare porous films having a total area of 315 cm 2 , and the film thickness and weight were measured.
In the measurement, the true density of the porous film was measured using a true density measuring device (BELPycno: manufactured by Microtrack Bell). The size of the measurement cell is 3.5 cc, and the obtained true density is D, the area of the porous film is S, the film thickness is d, and the weight is w, and the porosity is calculated by the following formula. bottom:
Porosity = (1-(w/(S x d x D) x 100 (1)
［最大応力］
　ＪＩＳ　Ｋ－６２５１－６号のサンプル形状の試験片を、２５℃(常温)の測定環境下において、引張り速度を１ｍｍ／ｍｉｎ．、チャック間距離を５０ｍｍとして測定を行い、フィルムが破断するまでのうち最も高い引張応力値（ＭＰａ）を最大応力とした。引張試験機は(島津製作所製：オートグラフAGS-50NX)を用いた。 [Maximum stress]
A sample-shaped test piece of JIS K-6251-6 was subjected to a tensile speed of 1 mm/min under a measurement environment of 25°C (normal temperature). , the distance between chucks was set to 50 mm, and the highest tensile stress value (MPa) until the film broke was taken as the maximum stress. A tensile tester (manufactured by Shimadzu Corporation: Autograph AGS-50NX) was used.
［弾性率］
　ＪＩＳ　Ｋ－６２５１－６号のサンプル形状の試験片を、２５℃（常温）の測定環境下において、引張り速度を１ｍｍ／ｍｉｎ、チャック間距離を５０ｍｍとして測定を行い、応力-ひずみ曲線において、初期の立ち上がり部の勾配から求めた。引張試験機は(島津製作所製：オートグラフAGS-50NX)を用いた。 [Elastic modulus]
A JIS K-6251-6 sample-shaped test piece was measured under a measurement environment of 25 ° C. (room temperature) at a tensile speed of 1 mm / min and a distance between chucks of 50 mm. It was obtained from the gradient of the rising part of A tensile tester (manufactured by Shimadzu Corporation: Autograph AGS-50NX) was used.
［伸び］
　ＪＩＳ　Ｋ－６２５１－６号のサンプル形状の試験片を、２５℃(常温)の測定環境下において、引張り速度を１ｍｍ／ｍｉｎ、チャック間距離を５０ｍｍとして測定を行い、フィルムが破断した際の破断ひずみを伸びとした。引張試験機は(島津製作所製：オートグラフAGS-50NX)を用いた。 [stretch]
A JIS K-6251-6 sample-shaped test piece was measured under a measurement environment of 25°C (room temperature) at a tensile speed of 1 mm/min and a distance between chucks of 50 mm. Strain was taken as elongation. A tensile tester (manufactured by Shimadzu Corporation: Autograph AGS-50NX) was used.
［破断エネルギー］
　島津製作所製：オートグラフAGS-50NXを用い、ＪＩＳ　Ｋ－６２５１－６号のサンプル形状の試験片を、２５℃（常温）の測定環境下において、引張り速度を１ｍｍ／ｍｉｎ、チャック間距離を５０ｍｍとして測定を行い、前記試験条件を島津製作所製オートグラフ用ソフトウェアTRAPEZIUM　LITE　Xを用いて引張試験を行った際に計算される「試験力-変位量の曲線」のデータを取得し、フィルムが破断するまでの当該データの積分値を破断エネルギー［Ｊ］とし、単位膜厚当たりの破断エネルギー［Ｊ／ｍｍ］を以下の式を用いて算出した：
単位膜厚当たりのエネルギー［Ｊ／ｍｍ］＝エネルギー［Ｊ］／測定フィルムの膜厚［ｍｍ］ [Breaking energy]
Shimadzu Corporation: Using Autograph AGS-50NX, a test piece of sample shape of JIS K-6251-6 is measured in a 25 ° C (normal temperature) environment at a tensile speed of 1 mm / min and a distance between chucks of 50 mm. Measurement was performed as above, and the data of the "test force-displacement curve" calculated when the tensile test was performed using the Shimadzu Autograph software TRAPEZIUM LITE X under the above test conditions was obtained, and the film fractured. The rupture energy [J] was defined as the integral value of the data until the rupture energy [J/mm] per unit film thickness was calculated using the following formula:
Energy per unit film thickness [J/mm] = energy [J]/measured film thickness [mm]
［リチウム反応量の測定］
　ポリイミド多孔質フィルムにおけるリチウム反応量ないし吸着量について、以下の手順に従って測定した。ポリイミド多孔質フィルムへのリチウムの反応量を測ることにより、ポリイミド多孔質フィルムを蓄電デバイスのセパレータとして用いるときの適性を評価することができる。ポリイミド多孔質フィルムにおけるリチウム反応量ないし吸着量の測定手順は以下の工程を有する：
（１）一対の電極間に、評価対象である多孔質フィルム、隔膜、およびシート状のリチウム供給源を順に重ねた積層体を準備する工程、
（２）前記積層体を筐体内に内容させ、この筐体に電解液を封入して評価セルを作製する工程、および
（３）電極を介して通電して多孔質フィルムに吸着ないし反応したリチウムの量を算出する工程。 [Measurement of Lithium Reaction Amount]
The reaction amount or adsorption amount of lithium in the polyimide porous film was measured according to the following procedure. By measuring the reaction amount of lithium to the polyimide porous film, the suitability of using the polyimide porous film as a separator of an electric storage device can be evaluated. The procedure for measuring the lithium reaction amount or adsorption amount in the polyimide porous film has the following steps:
(1) A step of preparing a laminate in which a porous film to be evaluated, a diaphragm, and a sheet-like lithium source are stacked in order between a pair of electrodes;
(2) a step of placing the laminate in a housing and sealing an electrolytic solution in the housing to prepare an evaluation cell; calculating the amount of
　（１）積層体を準備する工程
　図１に示すように、積層体１に用いる一対の電極３ａ、３ｂの材質や種類に特に制限はない。電極３ａ、３ｂの材質としては、例えば、銅、アルミニウム、銀、亜鉛などを用いることができる。電極３ａ、３ｂの形状としては、多孔質フィルム５、隔膜７、及びリチウム供給源１０を挟持することができる形状であればよく、例えば、円形薄板状、方形状など適宜きめるとよい。
　ここでは多孔質フィルム５としてポリイミド多孔質フィルムにおけるリチウムの吸着ないし反応量を測定することを目的としており、リチウムがポリイミド多孔質フィルム５に吸着するメカニズムの詳細は明らかではないが、樹脂の芳香環部分にリチウムが結合ないし配位するのではないかと考えられる。
　芳香環を有する樹脂はチウムが吸着しやすい傾向があり、この評価方法を用いてリチウムの吸着量ないし反応量を評価することで、負極として金属リチウムを用いるリチウム金属電池に適用できるかどうか判断の目安を得られる。リチウム電池用にポリイミド多孔質フィルムを用いる場合はリチウム反応量が少ない方が好ましく、従来からよく知られているＢＰＤＡ／ＰＤＡを用いたポリイミド多孔質フィルムではリチウム反応量が比較的多く、このためリチウムイオン電池やリチウム金属電池の初期におけるクーロン効率などに悪影響が及ぶ。本発明のポリイミド多孔質フィルムはリチウム反応量を低減しており、リチウムイオン電池やリチウム金属電池のクーロン効率を悪化させることはない。 (1) Step of Preparing Laminate As shown in FIG. 1, the materials and types of the pair of electrodes 3a and 3b used in the laminate 1 are not particularly limited. As materials for the electrodes 3a and 3b, for example, copper, aluminum, silver, zinc, or the like can be used. The electrodes 3a and 3b may have any shape as long as they can hold the porous film 5, the diaphragm 7, and the lithium supply source 10 therebetween.
Here, the purpose is to measure the adsorption or reaction amount of lithium in the polyimide porous film as the porous film 5, and the details of the mechanism by which lithium adsorbs to the polyimide porous film 5 are not clear. It is thought that lithium is bound or coordinated to the portion.
Resins with aromatic rings tend to adsorb thium, and by evaluating the amount of lithium adsorbed or reacted using this evaluation method, it is possible to determine whether the resin can be applied to lithium metal batteries that use metallic lithium as the negative electrode. You can get an estimate. When using a polyimide porous film for a lithium battery, it is preferable that the lithium reaction amount is small, and the conventionally well-known polyimide porous film using BPDA/PDA has a relatively large lithium reaction amount. The initial coulombic efficiency of ion batteries and lithium metal batteries is adversely affected. The polyimide porous film of the present invention reduces the reaction amount of lithium and does not deteriorate the coulombic efficiency of lithium ion batteries and lithium metal batteries.
　評価対象である多孔質フィルム５の多孔化の手法に特に制限はない。例えば、ポリアミック酸溶液に微粒子を分散したスラリーを準備し、このスラリーを薄膜状に形成した後に微粒子を除去することで多孔質フィルム５を取得する方法などが挙げられる。
　多孔質フィルム５の厚みや空孔率は特に限定はないが、複数の多孔質フィルムについてリチウムの反応量ないし吸着量を比較する場合は、多孔質フィルムの厚み、空孔率を合わせるとよい。この実施例では例えば膜厚２０μｍ、空孔率６５％に合わせているが、これに限らず膜厚１２μｍ、空孔率６０％などでももちろんかまわない。
　この多孔質フィルム５は、ニッケル箔１３上に設けるとよい。例えば、ニッケル箔１３上にスラリーを薄膜形成した後に微粒子を除去してニッケル箔上に多孔質フィルム５を設けてもよいし、ニッケル箔１３上に多孔質フィルム５を貼付したものを用いてもよい。ただし、ニッケル箔１３上に既に多孔化された多孔質フィルム５を貼り付ける場合は、多孔質フィルム５とニッケル箔１３との間の導電性を確保する必要がある。 There is no particular limitation on the technique for making the porous film 5 to be evaluated porous. For example, there is a method of obtaining the porous film 5 by preparing a slurry in which fine particles are dispersed in a polyamic acid solution, forming the slurry into a thin film, and then removing the fine particles.
The thickness and porosity of the porous film 5 are not particularly limited, but when comparing the reaction amount or adsorption amount of lithium for a plurality of porous films, the thickness and porosity of the porous films should be matched. In this embodiment, for example, the film thickness is adjusted to 20 μm and the porosity is 65%.
This porous film 5 is preferably provided on the nickel foil 13 . For example, after forming a thin film of slurry on the nickel foil 13, the porous film 5 may be provided on the nickel foil by removing the fine particles, or the porous film 5 may be attached on the nickel foil 13. good. However, when the porous film 5 that has already been made porous is pasted on the nickel foil 13 , it is necessary to ensure electrical conductivity between the porous film 5 and the nickel foil 13 .
　隔膜７は、評価セル内の一対の電極どうしが接触することを防ぐことができる絶縁膜であり、かつ電解液のイオン伝導性を確保できるものであればよく、例えばポリオレフィン微多孔膜をこの評価セルの隔膜７として用いるとよい。
　隔膜７に重ねるシート状に形成されたリチウム供給源１０としては例えばリチウム製の板ないし箔１５を用いるとよい。リチウム製の板や箔１７を用いる場合は、銀、銅、又はアルミニウムから選択される導体基板１７上に、リチウム金属層１５を一体的に層設したものを作製するとよい。
　多孔質フィルム５、隔膜７、及びリチウム供給源１０をこの順で積層した構造体を一対の電極３ａ、３ｂで挟持した構造体を作製する。このとき、多孔質フィルム５におけるニッケル箔１３を電極３ａに対向させ、多孔質フィルム５を隔膜７に対向させる。リチウム供給源１０は、銅やニッケルなどの導体基板１７を電極３ｂに対向させ、リチウム金属層１５を隔膜７に対向させるように配置する。このようにして積層体１を作製することができる。 The diaphragm 7 is an insulating film that can prevent the pair of electrodes in the evaluation cell from coming into contact with each other, and can ensure the ionic conductivity of the electrolytic solution. It may be used as the diaphragm 7 of the cell.
As the sheet-shaped lithium supply source 10 to be placed on the diaphragm 7, for example, a plate or foil 15 made of lithium may be used. When a plate or foil 17 made of lithium is used, it is preferable to prepare a lithium metal layer 15 integrally formed on a conductor substrate 17 selected from silver, copper, or aluminum.
A structure is prepared by sandwiching a structure in which a porous film 5, a diaphragm 7, and a lithium supply source 10 are laminated in this order between a pair of electrodes 3a and 3b. At this time, the nickel foil 13 in the porous film 5 is made to face the electrode 3a, and the porous film 5 is made to face the diaphragm 7 . The lithium supply source 10 is arranged such that a conductor substrate 17 such as copper or nickel faces the electrode 3b, and the lithium metal layer 15 faces the diaphragm 7. As shown in FIG. Thus, the laminated body 1 can be produced.
　（２）積層体を筐体内に内容させ、この筐体に電解液を封入して評価セルを作製する工程
　積層体１を準備した後、この積層体１を容器内に収容し、この容器内に電解液を注入し封止する。
　この容器は、一般的な電池用の外装体に用いられるものを任意に使用することができる。この実施例ではラミネート型の電池を作製するための樹脂製のラミネートフィルムを外装体として用いたが、それ以外にも例えば、コイン電池を作製するための金属製外装体などを用いることもできる。コイン電池用の外装体を構成する材料としてはステンレスやアルミニウムが好適であり、ステンレス板やアルミニウム板をプレス加工して所望する形状に形成するとよい。 (2) Step of placing the laminate in a housing and enclosing an electrolytic solution in the housing to prepare an evaluation cell After preparing the laminate 1, the laminate 1 is placed in a container, The electrolyte is injected into and sealed.
As the container, any one used for a general outer package for batteries can be used. In this example, a resin laminate film for producing a laminate type battery was used as the outer packaging, but in addition to this, for example, a metal outer packaging for producing a coin battery can also be used. Stainless steel or aluminum is suitable as a material for forming the exterior body for a coin battery, and it is preferable to press a stainless steel plate or an aluminum plate into a desired shape.
　評価セル内に封入する電解液にも制限はなく、例えば、ＬｉＰＦ６などのリチウム塩をエチレンカーボネート（ＥＣ）やジエチルカーボネート（ＤＥＣ）などの有機溶媒に溶解させた有機電解液でよい。リチウム塩としてＬｉＦＳＩを用いて評価してもよい。 The electrolyte to be enclosed in the evaluation cell is also not limited, and may be, for example, an organic electrolyte in which a lithium salt such as LiPF 6 is dissolved in an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC). You may evaluate using LiFSI as a lithium salt.
　評価セルは、各部材を時前に乾燥することが好ましい。乾燥方法は、各部材の材質毎に影響が出ない条件であればよい。また積層体１を筐体内に内容させたあと注液前に全ての部材に影響が出ない条件で改めて乾燥させるとなお良い。なお、評価対象である多孔質フィルム５の厚み、空孔率、厚み、孔径などは同一条件に揃えることが望ましい。例えば、電極の種類、」厚み、大きさ、多孔質フィルムがニッケル箔を有する場合のニッケル箔の大きさ及び厚み、セパレータの種類及び大きさ、リチウム供給源、評価サンプルの乾燥条件など、種々の条件を揃えることでより厳密な評価が可能となる。 It is preferable to dry the evaluation cell before each member is used. Any drying method may be used as long as it does not affect the material of each member. Further, after the laminate 1 is placed in the housing, it is more preferable to dry again under conditions that do not affect all the members before pouring the liquid. It is desirable that the thickness, porosity, thickness, pore size, etc. of the porous film 5 to be evaluated be the same. For example, the type of electrode, thickness, size, size and thickness of nickel foil when the porous film has nickel foil, type and size of separator, lithium supply source, drying conditions for evaluation samples, etc. By arranging the conditions, a more rigorous evaluation becomes possible.
　（３）電極を介して通電して多孔質フィルムに吸着ないし反応したリチウムの量を算出する工程
　電極３ａ、３ｂを介して評価セルを通電する。このときリチウム供給源１０から多孔質フィルム５にリチウムが供給され、多孔質フィルム５にリチウムが反応ないし吸着される。通電工程は、定電流・定電圧で行う（ＣＣＣＶ）。
　例えば０．１３ｍＡなど予め定められた電流値で通電する（ＣＣ）。電圧が一定の値（例えば０．０１V）に到達した後は、電流値が例えば０．０２６ｍＡとなるまで行う。
　この通電工程により電気容量を算出し、これによりポリイミド多孔質フィルム５がリチウムと反応ないし吸着した量を求めることができる。 (3) Step of Calculating the Amount of Lithium Adsorbed or Reacted to the Porous Film by Passing Electric Power Through the Electrodes The evaluation cell is energized through the electrodes 3a and 3b. At this time, lithium is supplied from the lithium supply source 10 to the porous film 5 and reacted or adsorbed on the porous film 5 . The energization step is performed at constant current and constant voltage (CCCV).
For example, current is supplied at a predetermined current value such as 0.13 mA (CC). After the voltage reaches a certain value (for example, 0.01 V), the current value reaches, for example, 0.026 mA.
An electric capacity is calculated by this energization step, and the amount of lithium that the polyimide porous film 5 reacts with or adsorbs can be obtained.
　上述したように、（１）～（３）の手順に沿ってポリイミド多孔質フィルム５にリチウムと反応ないし吸着した量を測定することができる。ポリイミド多孔質フィルム５にリチウムと反応ないし吸着する性質がないのであれば、充電工程においてリチウムがポリイミド多孔質フィルム５に反応ないし吸着することがなく、このため通電工程で電流がほぼ流れない。
　他方、ポリイミド多孔質フィルム５がリチウムと反応ないし吸着する性質を有する場合は、通電工程においてリチウムがポリイミド多孔質フィルム５に反応ないし吸着し、このため電流が流れる。
　ポリイミド多孔質フィルム５をリチウムイオン電池やリチウム金属電池用のセパレータとして用いる場合は、このリチウムと反応ないし吸着する性質が全くないか、より小さい方が好ましい。 As described above, the amount of lithium reacted with or adsorbed on the polyimide porous film 5 can be measured according to the procedures (1) to (3). If the polyimide porous film 5 does not have the property of reacting with or adsorbing lithium, lithium will not react with or adsorb to the polyimide porous film 5 in the charging process, and therefore almost no current will flow in the energizing process.
On the other hand, when the polyimide porous film 5 has the property of reacting with or adsorbing lithium, lithium reacts with or adsorbs to the polyimide porous film 5 in the current-applying step, so that current flows.
When the polyimide porous film 5 is used as a separator for a lithium ion battery or a lithium metal battery, it is preferable that the property of reacting with or adsorbing lithium is completely absent or less.
実施例１
［ポリアミック酸の準備］
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに４，４’－オキシジアニリンを：１．９１５ｇとピロメリット酸無水物：２．０８６ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
［ポリイミド多孔質フィルムの準備］
　ポリアミック酸と粒径４００ｎｍのポリスチレン樹脂粒子とを混合して作成されたスラリーをNi箔上に塗工し多孔化した。ニッケル箔上に多孔質ポリイミド層を層設したものを直径１４ｍｍの円形に打ち抜き一晩真空乾燥した。多孔化されたポリイミド多孔質フィルム層は厚み２０μｍ、空孔率６５％であった。
［隔膜の準備］
　ポリオレフィン性フィルム（セルガード（登録商標）２３４０）をＰＥＴ製フィルムに挟んで直径１８ｍｍの円形に打ち抜き一晩真空乾燥した。
［リチウム供給源の準備］
　銅箔上に厚さ２０μｍとなるように圧延されたリチウム金属層を有するシートを直径１６ｍｍの円形に打ち抜いた。
［積層体の準備］
　多孔質ポリイミドフィルム、隔膜、及びシート状のリチウム供給源を、それぞれの中心が合うように積層し、さらに一対の電極で挟み積層体を作製した。電極としては、直径１６ｍｍの円板状の銅板を用いた。
　ポリイミド多孔質フィルムは、ニッケル箔を電極に対向させ、多孔質ポリイミド層を隔膜と対向させた。またリチウム供給源は、リチウム金属層を隔膜と対向させ、銅箔を電極と対向させた。
［評価セルの作製］
　電極に溶接したリードが外部に突出するように構成されたラミネート材の外装体に、積層体を内容させ、この外装体内に１５０μｌの電解液を入れ封入した。電解液としては、ＥＣ：ＤＥＣが１：１の割合（ｖｏｌ％）になるように混合した混合溶媒に、ＬｉＰＦ６を１Ｍとなるように溶解させたものを用いた。
［初期充放電特性の評価］
　上述のように作製した評価セルについて以下の試験条件に従い試験を実施し、ポリイミド多孔質フィルムにおけるリチウムの反応ないし吸着量を測定した。測定結果を表１に示す。
［充放電試験条件］
１）充放電試験機：ＴＯＳＣＡＴ－３０００（東洋システム株式会社製）
２）恒温槽：ＬＵ－１１３（エスペック株式会社製）を用いて２５℃に設定
３）充放電条件
定電流・定電圧モード０．１Ｖ、０．１３ｍＡ、カットオフ ０．０２６ｍＡ Example 1
[Preparation of polyamic acid]
To 16 g of N,N-dimethylacetamide, 1.915 g of 4,4'-oxydianiline and 2.086 g of pyromellitic anhydride were added, and the mixture was stirred in a separable flask at 25°C for 12 hours. It was made to react and polyamic acid was obtained.
[Preparation of polyimide porous film]
A slurry prepared by mixing polyamic acid and polystyrene resin particles with a particle size of 400 nm was coated on a Ni foil to make it porous. A circle having a diameter of 14 mm was punched out from a nickel foil on which a porous polyimide layer was formed, and vacuum-dried overnight. The polyimide porous film layer made porous had a thickness of 20 μm and a porosity of 65%.
[Preparation of Diaphragm]
A polyolefinic film (Celgard (registered trademark) 2340) was sandwiched between PET films, punched into a circle with a diameter of 18 mm, and vacuum-dried overnight.
[Preparation of lithium supply source]
A sheet having a lithium metal layer rolled to a thickness of 20 μm on a copper foil was punched into a circle with a diameter of 16 mm.
[Preparation of laminate]
A porous polyimide film, a diaphragm, and a sheet-like lithium supply source were laminated so that their respective centers were aligned, and sandwiched between a pair of electrodes to produce a laminate. A disk-shaped copper plate with a diameter of 16 mm was used as the electrode.
For the polyimide porous film, the nickel foil was opposed to the electrode, and the porous polyimide layer was opposed to the diaphragm. In the lithium supply source, the lithium metal layer was opposed to the diaphragm and the copper foil was opposed to the electrode.
[Production of evaluation cell]
The laminated body was enclosed in an outer package made of a laminated material in which the leads welded to the electrodes protruded outward, and 150 μl of an electrolytic solution was put and sealed in the outer package. As the electrolytic solution, a solution obtained by dissolving LiPF 6 to 1M in a mixed solvent in which EC:DEC was mixed at a ratio (vol %) of 1:1 was used.
[Evaluation of initial charge/discharge characteristics]
The evaluation cell produced as described above was tested under the following test conditions, and the amount of reaction or adsorption of lithium in the polyimide porous film was measured. Table 1 shows the measurement results.
[Charge/discharge test conditions]
1) Charge/discharge tester: TOSCAT-3000 (manufactured by Toyo System Co., Ltd.)
2) Constant temperature bath: LU-113 (manufactured by Espec Co., Ltd.) set at 25 ° C. 3) Charging and discharging conditions Constant current/constant voltage mode 0.1 V, 0.13 mA, cutoff 0.026 mA
実施例２
　ジアミンとしてp－フェニレンジアミン：０．５８１ｇおよび４，４’－オキシジアニリンを：１．０７６ｇ用い、カルボン酸としてピロメリット酸無水物：２．３４３ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。なおいずれの実施例および比較例に示したポリアミック酸を用いて製膜および多孔化することができた。 Example 2
In the same manner as in Example 1 except that 0.581 g of p-phenylenediamine and 1.076 g of 4,4'-oxydianiline were used as diamines, and 2.343 g of pyromellitic anhydride was used as carboxylic acid. Li reaction amount was measured. It should be noted that the polyamic acid shown in any of the examples and comparative examples could be used to form a film and make it porous.
実施例３
　ジアミンとしてp－フェニレンジアミン：０．３３２ｇおよび４，４’－オキシジアニリンを：１．４３５ｇ用い、カルボン酸としてピロメリット酸無水物：２．２３３ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。なおいずれの実施例および比較例に示したポリアミック酸を用いて製膜および多孔化することができた。 Example 3
In the same manner as in Example 1 except that 0.332 g of p-phenylenediamine and 1.435 g of 4,4'-oxydianiline were used as diamines, and 2.233 g of pyromellitic anhydride was used as carboxylic acid. Li reaction amount was measured. It should be noted that the polyamic acid shown in any of the examples and comparative examples could be used to form a film and make it porous.
実施例４
　ジアミンとしてp－フェニレンジアミン：０．１０６ｇおよび４，４’－オキシジアニリンを：１．７６２ｇ用い、カルボン酸としてピロメリット酸無水物：２．１３２ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。なおいずれの実施例および比較例に示したポリアミック酸を用いて製膜および多孔化することができた。 Example 4
In the same manner as in Example 1 except that 0.106 g of p-phenylenediamine and 1.762 g of 4,4'-oxydianiline were used as diamines, and 2.132 g of pyromellitic anhydride was used as carboxylic acid. Li reaction amount was measured. It should be noted that the polyamic acid shown in any of the examples and comparative examples could be used to form a film and make it porous.
実施例５
　ジアミンとして２，２’－ジメチルベンジジン：１．９７３ｇを用い、カルボン酸としてピロメリット酸無水物：２．０２７ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Example 5
The reaction amount of Li was measured in the same manner as in Example 1 except that 1.973 g of 2,2'-dimethylbenzidine was used as the diamine and 2.027 g of pyromellitic anhydride was used as the carboxylic acid.
実施例６
　ジアミンとして２，２’－ジメチルベンジジン：１．３９３ｇおよび４，４’－オキシジアニリンを：０．５６３ｇ用い、カルボン酸としてピロメリット酸無水物：２．０４４ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Example 6
2,2′-dimethylbenzidine: 1.393 g and 4,4′-oxydianiline: 0.563 g were used as diamines, and pyromellitic anhydride: 2.044 g was used as carboxylic acid. Li reaction amount was measured in the same manner.
実施例７
　ジアミンとしてp－フェニレンジアミン：０．５２７ｇおよび４，４’－オキシジアニリンを：０．９７６ｇ用い、カルボン酸としてピロメリット酸無水物：１．０６３ｇおよび３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：１．４３４ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Example 7
0.527 g of p-phenylenediamine and 0.976 g of 4,4'-oxydianiline were used as diamines, and 1.063 g of pyromellitic anhydride and 3,3',4,4'-biphenyl were used as carboxylic acids. The reaction amount of Li was measured in the same manner as in Example 1 except that 1.434 g of tetracarboxylic dianhydride was used.
実施例８
　ジアミンとしてp－フェニレンジアミン：０．１７６ｇおよび４，４’－オキシジアニリンを：１．３０２ｇ用い、カルボン酸として４，４’－オキシジフタル酸無水物：２．５２２ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Example 8
Example 1 except that 0.176 g of p-phenylenediamine and 1.302 g of 4,4'-oxydianiline were used as diamines, and 2.522 g of 4,4'-oxydiphthalic anhydride was used as carboxylic acid. Li reaction amount was measured in the same manner as above.
実施例９
　ジアミンとしてp－フェニレンジアミン：０．４５４ｇおよび４，４’－ジアミノジフェニルエーテルを：０．８４１ｇ用い、カルボン酸として３，３’，４，４’－ベンゾフェノンテトラカルボン酸二無水物：２．７０５ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Example 9
0.454 g of p-phenylenediamine and 0.841 g of 4,4'-diaminodiphenyl ether were used as the diamine, and 2.705 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride was used as the carboxylic acid. The reaction amount of Li was measured in the same manner as in Example 1, except that it was used.
実施例１０
　ジアミンとして２，２’－ジメチルベンジジン：１．６７７ｇを用い、カルボン酸として３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：２．３２４ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Example 10
Same as Example 1 except that 2,2'-dimethylbenzidine: 1.677 g was used as the diamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride: 2.324 g was used as the carboxylic acid. Then, the Li reaction amount was measured.
比較例１
　ジアミンとしてp－フェニレンジアミン：１．０７５ｇを用い、カルボン酸として３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：２．９２５ｇを用いた以外は実施例１と同様にしてＬｉ反応量を測定した。 Comparative example 1
Li The reaction volume was measured.
Figure JPOXMLDOC01-appb-T000001
  
Figure JPOXMLDOC01-appb-T000001
  
　後述するが、表１に記載されたポリアミック酸を参照して調製したスラリーをもとに原反を作製し、さらにこの原反を焼成してポリイミド多孔質フィルムを作製した。なお微粒子には４００nmの粒径を有するポリスチレン製の樹脂粒子を用いた。詳細を以下に記載する。 As will be described later, a raw film was produced based on a slurry prepared with reference to the polyamic acids listed in Table 1, and this raw film was baked to produce a polyimide porous film. Polystyrene resin particles having a particle size of 400 nm were used as the fine particles. Details are given below.
実施例Ｓ１
［ポリアミック酸の準備］
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに２，２’－ジメチルベンジジン：１．９７２９ｇおよびピロメリット酸無水物：２．０２７１ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００nmのポリスチレン粒子を５．４９３０ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に膜状に吐出した。この支持体上の未焼成膜を乾燥させて剥離し、焼成炉にて熱処理して粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍであった。またガーレ値は８６．１秒、Ｌｉ反応量は７０ｍＡｈ／ｇであった。物性については表２にまとめた。なお、後述の実施例Ｓ２～６および比較例Ｃ１、２も表２にまとめた。 Example S1
[Preparation of polyamic acid]
1.9729 g of 2,2′-dimethylbenzidine and 2.0271 g of pyromellitic anhydride were added to 16 g of N,N-dimethylacetamide, and the mixture was stirred in a separable flask at 25° C. for 12 hours to react. , to obtain polyamic acid.
A slurry was prepared by adding 5.4930 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die. The unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film. The porosity was approximately 65% and the film thickness was 20 μm. The Gurley value was 86.1 seconds, and the Li reaction amount was 70 mAh/g. The physical properties are summarized in Table 2. Examples S2 to S6 and Comparative Examples C1 and C2, which will be described later, are also summarized in Table 2.
実施例Ｓ２
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに４，４’－オキシジアニリン：０．５６３０ｇ、２，２’－ジメチルベンジジン：１．３９２７ｇ、およびピロメリット酸無水物：２．０４４３ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００ｎｍのポリメチルメタクリレート粒子を６．２２５ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に吐出して原反を作製した。熱処理にてポリメチルメタクリレート粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍ、ガーレ値は８９．４秒、Ｌｉ反応量は５５ｍＡｈ／ｇであった。 Example S2
N,N-dimethylacetamide: 0.5630 g of 4,4'-oxydianiline, 1.3927 g of 2,2'-dimethylbenzidine, and 2.0443 g of pyromellitic anhydride were added to 16 g of separable The mixture was stirred in a flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
A slurry was prepared by adding 6.225 g of polymethyl methacrylate particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged onto a support from a T-die to produce a raw roll. Polymethyl methacrylate particles were removed by heat treatment to produce a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 μm, the Gurley value was 89.4 seconds, and the Li reaction amount was 55 mAh/g.
実施例Ｓ３
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに２，２’－ジメチルベンジジン：１．６７６５ｇおよび３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：２．３２３５ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００ｎｍのポリメチルメタクリレート粒子を６．２２５ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に吐出して原反を作製した。熱処理にてポリメチルメタクリレート粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍ、ガーレ値は１００秒、Ｌｉ反応量は３３０ｍＡｈ／ｇであった。 Example S3
N,N-dimethylacetamide: 16 g of 2,2'-dimethylbenzidine: 1.6765 g and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride: 2.3235 g were added, and a separable flask was added. The mixture was stirred at 25° C. for 12 hours for reaction to obtain a polyamic acid.
A slurry was prepared by adding 6.225 g of polymethyl methacrylate particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged onto a support from a T-die to produce a raw roll. Polymethyl methacrylate particles were removed by heat treatment to produce a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 μm, the Gurley value was 100 seconds, and the Li reaction amount was 330 mAh/g.
実施例Ｓ４
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：１．７２８ｇ、ピロメリット酸無水物：０．８５４ｇ、p-フェニレンジアミン：０．６３５ｇ、および４，４’－オキシジアニリン：０．７８４ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００nmのポリスチレン粒子を５．４９３ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に膜状に吐出した。この支持体上の未焼成膜を乾燥させて剥離し、焼成炉にて熱処理して粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍであった。 Example S4
N,N-dimethylacetamide: 16 g, 3,3′,4,4′-biphenyltetracarboxylic dianhydride: 1.728 g, pyromellitic anhydride: 0.854 g, p-phenylenediamine: 0.635 g, and 4,4′-oxydianiline: 0.784 g were added and stirred in a separable flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
A slurry was prepared by adding 5.493 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die. The unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film. The porosity was approximately 65% and the film thickness was 20 μm.
実施例Ｓ５
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：１．４３４ｇ、ピロメリット酸無水物：１．０６３ｇ、p-フェニレンジアミン：０．５２７ｇ、および４，４’－オキシジアニリン：０．９７６ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００nmのポリスチレン粒子を５．４９３ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に膜状に吐出した。この支持体上の未焼成膜を乾燥させて剥離し、焼成炉にて熱処理して粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍ、ガーレ値は１００秒、Ｌｉ反応量は１９９ｍＡｈ／ｇであった。 Example S5
N,N-dimethylacetamide: 16 g, 3,3′,4,4′-biphenyltetracarboxylic dianhydride: 1.434 g, pyromellitic anhydride: 1.063 g, p-phenylenediamine: 0.527 g, and 4,4′-oxydianiline: 0.976 g were added and stirred in a separable flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
A slurry was prepared by adding 5.493 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die. The unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film. The porosity was about 65%, the film thickness was 20 μm, the Gurley value was 100 seconds, and the Li reaction amount was 199 mAh/g.
実施例Ｓ６
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：１．１４３ｇ、ピロメリット酸無水物：１．２７１ｇ、p-フェニレンジアミン：０．４２０ｇ、および４，４’－オキシジアニリン：１．１６７ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００nmのポリスチレン粒子を５．４９３ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に膜状に吐出した。この支持体上の未焼成膜を乾燥させて剥離し、焼成炉にて熱処理して粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍであった。 Example S6
N,N-dimethylacetamide: 16 g, 3,3',4,4'-biphenyltetracarboxylic dianhydride: 1.143 g, pyromellitic anhydride: 1.271 g, p-phenylenediamine: 0.420 g, and 4,4′-oxydianiline: 1.167 g were added and stirred in a separable flask at 25° C. for 12 hours for reaction to obtain a polyamic acid.
A slurry was prepared by adding 5.493 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged in the form of a film onto a support from a T-die. The unsintered film on the support was dried, peeled off, and heat treated in a sintering furnace to remove particles to produce a polyimide porous film. The porosity was approximately 65% and the film thickness was 20 μm.
比較例Ｃ１
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに３，３’，４，４’－ビフェニルテトラカルボン酸ニ無水物：２．９２４９ｇとp-フェニレンジアミン：１．０７５１ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００nmのポリスチレン粒子を５．４９３０ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に吐出し、熱処理にて粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍ、ガーレ値は１００秒、Ｌｉ反応量は１２７５ｍＡｈ／ｇであった。 Comparative example C1
2.9249 g of 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 1.0751 g of p-phenylenediamine were added to 16 g of N,N-dimethylacetamide, and the mixture was placed in a separable flask for 25 minutes. C. for 12 hours and reacted to obtain a polyamic acid.
A slurry was prepared by adding 5.4930 g of polystyrene particles having a particle size of 400 nm to this polyamic acid, and the slurry was discharged from a T-die onto a support, and the particles were removed by heat treatment to prepare a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 μm, the Gurley value was 100 seconds, and the Li reaction amount was 1275 mAh/g.
比較例Ｃ２
　Ｎ，Ｎ－ジメチルアセトアミド：１６ｇに４，４’－オキシジアニリン：１．９１４５ｇおよびピロメリット酸無水物：２．０８５５ｇを添加し、セパラブルフラスコ中にて２５℃で１２時間攪拌して反応させ、ポリアミック酸を得た。
　このポリアミック酸に粒径４００ｎｍのポリメチルメタクリレート粒子を６．１２０７ｇ加えてスラリーを調製し、このスラリーをTダイから支持体上に吐出して原反を作製した。熱処理にてポリメチルメタクリレート粒子を除去しポリイミド多孔質フィルムを作製した。空孔率は略６５％、膜厚は２０μｍ、ガーレ値は６４．１秒、Ｌｉ反応量は７３ｍＡｈ／ｇであった。 Comparative example C2
1.9145 g of 4,4'-oxydianiline and 2.0855 g of pyromellitic anhydride were added to 16 g of N,N-dimethylacetamide, and the mixture was stirred in a separable flask at 25°C for 12 hours to react. to obtain polyamic acid.
A slurry was prepared by adding 6.1207 g of polymethyl methacrylate particles having a particle size of 400 nm to this polyamic acid, and this slurry was discharged onto a support from a T-die to produce a raw roll. Polymethyl methacrylate particles were removed by heat treatment to produce a polyimide porous film. The porosity was approximately 65%, the film thickness was 20 μm, the Gurley value was 64.1 seconds, and the Li reaction amount was 73 mAh/g.
Figure JPOXMLDOC01-appb-T000002
  
Figure JPOXMLDOC01-appb-T000002
  

Claims (8)

  1. 　カルボン酸とジアミンとの共重合体で構成され、多数の細孔が形成されたポリイミド多孔質フィルムであって、
    　前記ジアミンとして、ジメチルベンジジンを含有することを特徴とするポリイミド多孔質フィルム。     A polyimide porous film composed of a copolymer of a carboxylic acid and a diamine and having a large number of pores,
    A polyimide porous film containing dimethylbenzidine as the diamine.
  2. 　カルボン酸としてピロメリット酸二無水物およびビフェニルテトラカルボン酸二無水物の少なくともどちらか一方を含む請求項１に記載のポリイミド多孔質フィルム。 The polyimide porous film according to claim 1, which contains at least one of pyromellitic dianhydride and biphenyltetracarboxylic dianhydride as a carboxylic acid.
  3. 　前記細孔の孔径が８００ナノメートル以下である請求項１または２に記載のポリイミド多孔質フィルム。 The polyimide porous film according to claim 1 or 2, wherein the pores have a pore diameter of 800 nanometers or less.
  4. 　最大応力が２Ｎ／ｍｍ２以上である請求項３に記載のポリイミド多孔質フィルム。 4. The polyimide porous film according to claim 3, which has a maximum stress of 2 N/mm2 or more .
  5. 　破断エネルギーが０．３４Ｊ／ｍｍ以上である請求項４に記載のポリイミド多孔質フィルム。 The polyimide porous film according to claim 4, which has a breaking energy of 0.34 J/mm or more.
  6. 　蓄電デバイス用のセパレータである請求項５に記載のポリイミド多孔質フィルム。 The polyimide porous film according to claim 5, which is a separator for an electric storage device.
  7. 　請求項６に記載のポリイミド多孔質フィルムを、正極と負極との間に設けた、電極構造体。 An electrode structure in which the polyimide porous film according to claim 6 is provided between a positive electrode and a negative electrode.
  8. 　請求項７に記載の電極構造体を備えた、蓄電デバイス。 An electricity storage device comprising the electrode structure according to claim 7.
PCT/JP2022/040857 2021-11-01 2022-11-01 Polyimide porous film, electrode structure, and power storage device WO2023074909A1 (en)

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Publication number Priority date Publication date Assignee Title
CN102655228A (en) * 2012-05-08 2012-09-05 江苏科技大学 High-temperature-resisting polyimide cell diaphragm and preparation method thereof
CN108172740A (en) * 2017-12-27 2018-06-15 桂林电器科学研究院有限公司 High porosity polyimide diaphragm preparation method and products thereof
US20190058178A1 (en) * 2017-08-17 2019-02-21 Ohio Aerospace Institute Polyimide-network and polyimide-urea-network battery separator compositions
CN109473605A (en) * 2018-10-05 2019-03-15 中山大学 The preparation method of polyimide foraminous diaphragm
CN112062989A (en) * 2020-08-10 2020-12-11 航天特种材料及工艺技术研究所 Polyimide aerogel lithium battery diaphragm and preparation method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102655228A (en) * 2012-05-08 2012-09-05 江苏科技大学 High-temperature-resisting polyimide cell diaphragm and preparation method thereof
US20190058178A1 (en) * 2017-08-17 2019-02-21 Ohio Aerospace Institute Polyimide-network and polyimide-urea-network battery separator compositions
CN108172740A (en) * 2017-12-27 2018-06-15 桂林电器科学研究院有限公司 High porosity polyimide diaphragm preparation method and products thereof
CN109473605A (en) * 2018-10-05 2019-03-15 中山大学 The preparation method of polyimide foraminous diaphragm
CN112062989A (en) * 2020-08-10 2020-12-11 航天特种材料及工艺技术研究所 Polyimide aerogel lithium battery diaphragm and preparation method thereof

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